BRITISH SUB▼AQUA CLUB
Skill Development Course
Instructor
Notes
Issued September 2000
Search and
Recovery
 The British Sub-Aqua Club, Telford’s Quay, South Pier Road, Ellesmere Port, Cheshire CH65 4FY
BRITISH SUB ▼AQUA CLUB
Skill Development Courses
Instructor Notes Search and Recovery
COURSE OUTLINE
Course Introduction
15 mins
Theory Lesson
The Shot-line and its Uses
45 mins
Theory Lesson
Search Operations
45 mins
Practical Lesson
Shot-line Construction Workshop
60 mins
Practical Lesson
Search Techniques Dry Practice 1
25 mins
Practical Lesson
Search Techniques Dive 1
Practical Lesson
Search Techniques Dry Practice 2
Practical Lesson
Search Techniques Dive 2
Theory lesson
Recovery Operations
45 mins
Practical Lesson
Recovery Techniques
60 mins
Practical Lesson
Search and Recovery Dive 1
120 mins
Practical Lesson
Search and Recovery Dive 2
120 mins
Course Debrief and Open Forum
100 mins
25 mins
100 mins
30 mins
COURSE REQUIREMENTS
Course aims
The aims of this course are to instruct divers in the correct techniques
and procedures involved in search and recovery projects, and to provide practical experience of underwater search methods and the use
of buoyancy for lifting objects.
Administration
A course registration form should be completed and sent to BSAC HQ
a minimum of two weeks prior to the event. HQ will supply the appropriate courseware and a Course Report Form. After the course, the
completed Course Report Form should be returned without delay to
BSAC HQ, where the attendance of the students on the course will be
recorded on the membership database. Logbook certificates for students will be prepared, and sent to the address stipulated on the
Course Report Form for Branch and School-run events, and to the
individual students for Coaching Scheme-run events.
For Coaching Scheme courses, on completion of the course, fees,
accounts, expense claims, etc., should be forwarded to BSAC HQ.
Instructors
The course must be led by an instructor holding a minimum qualification
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Instructor Notes: Search and Recovery
of Open Water Instructor. Other staff instructors must hold a minimum
qualification of Club Instructor. All instructors must be Advanced
Divers and hold the Search and Recovery course logbook certificate.
They should also have practical experience of search and recovery
operations.
A minimum ratio of one Instructor to four students is required.
Lead Instructor’s responsibilities
The Lead Instructor has an important role in the quality control of the
event. It is the Lead Instructor’s responsibility to ensure that the event
is run in accordance with all the requirements, standards and syllabus, and that all instructors are fully up to date in their theory knowledge and in current practice. Where necessary, the Lead Instructor
should arrange for refresher training appropriate to the individual’s
needs, to be provided prior to the event.
Abnormal circumstances
Where abnormal circumstances arise (e.g. a potential instructor with
relevant qualifications from another agency), specific arrangements
will be considered. These arrangements must, however, be discussed
in advance with the Skills Development Course Adviser.
Students
Students must hold a minimum grade of BSAC Sports Diver or equivalent.
Student who have previously attended the Advanced Diving Technique course do not need to attend the Shot-line classroom lesson
and workshop as these are covered in both courses.
Outline
The above outline represents the logical arrangement of theory and
practical lessons. It can be run, either as a series of separate sessions
over a period of time or as a two-day event to suit the needs of
Branches, Schools, or the Coaching Scheme. However the course is
run, the mandatory requirement is that wet practical lessons are preceded by their associated dry practical lessons. These in turn must be
preceded by their associated theory lessons.
Visual aids
These notes are intended to be used in conjunction with the companion BSAC Visual Aids. Their use will help to ensure that a consistent
standard of lesson content is achieved on all courses. Indications of
their use are appended in the margin of these Notes, alongside the
appropriate lesson element. The Visual Aids are structured to display
key points, each of which should be further amplified by the instructor.
The Visual Aids are supplied as PowerPoint files. The files appropriate to each lesson are as follows:
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Course Introduction
The Shotline and its Uses
Search Operations
Recovery Operations
Intro.ppt
Shot.ppt
Search.ppt
Recovery.ppt
Each file concludes with a plain black slide. This is to avoid computer
presentations ending in a distracting and unsightly return to the PowerPoint screen. If printing hard copy slides for use on an OHP then this
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Instructor Notes: Search and Recovery
final slide should be omitted from the print selection.
Facilities and equipment
The course will require the use of a classroom adequate to hold the
number of participants for the ‘dry’ lessons. Dry practicals will require
an open area sufficient for the number of groups involved to practice
rigging shot-lines and conduct dry-runs of the search techniques.
For the ‘wet’ lessons, easy access to reasonably flat bottom in a depth
of 6–10 metres is required. The nature of the bottom should be such
that adequate visibility is maintained for both instructing and monitoring of students.
Instructors will require an appropriate selection of the following equipment both for use in the practical lessons and also to show as examples in the theory lessons:
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reels
lines
weights
buoys
containers to use for lifting
lifting bags of various shapes and sizes
lifting strops
karabiners.
Course documentation
At the end of the course all students should be issued with the Student
Pack containing a set of Student Notes.
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Instructor Notes: Search and Recovery
LESSON CONTENTS
These Notes represent advice, current at the time of writing. Should
this advice change at any time, such changes will be published on the
BSAC Web site and in other, periodically circulated documentation.
Where subsequent to the date of publication of these notes, any
changes will take precedence, until such time as the changes are
incorporated in the next updated version of these Notes. Instructors
should therefore ensure that they have the latest edition of these
Notes and are conversant with any relevant updates.
These Notes are not intended for use during lessons as prompt
sheets, but to enable instructors to prepare their own prompt sheets
in their preferred format.
Where courses are run outside the UK, some aspects of the course content will need adapting to reflect local procedures and standards. In these
circumstances, instructors should modify the information presented, so
that UK-specific information is replaced by the local equivalent.
VA Intro.1
COURSE INTRODUCTION
15 MINS
Start the course by introducing the staff and then briefly explain why
search and recovery techniques may be useful to amateur divers.
Give examples such as searching for and recovering a lost object, lost
anchor recovery or to locate a shipwreck.
Explain the objectives of the course:
to instruct divers in the correct techniques and procedures
involved in search and recovery projects
● to provide practical experience of underwater search methods
and the use of buoyancy for lifting objects.
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VA Intro.2
Explain the programme for the course and any implications of moving
from the classroom to the ‘dry’ and ‘wet’ practical sessions. You may
wish to add an additional visual aid to illustrate the programme that
you are going to follow.
VA Shot.1
THE SHOT-LINE AND ITS USES
45 MINS
VA Shot.2
Introduction
Briefly explain the topics that will be covered in this lesson and how
they will relate to the subsequent practical lessons.
What is a shot-line?
In its simplest form it is a line, marked by a conspicuous float on the
surface, and attached to a heavy weight or anchor/grapnel that positions the shot-line on the bottom – a ‘datum point’ both under water
and on the surface. This configuration has its limits, however, and so
other configurations have been developed for use under varying circumstances. These various configurations will be explained as the
lesson progresses.
VA Shot.3
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Instructor Notes: Search and Recovery
Why use a shot-line?
Explain the benefits of using a shot line:
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VA Shot.4
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gets divers directly to the target – often not possible with free
descent (e.g. to a wreck). It also provides the shortest route
from/to the surface thus saving dive time!
reference line when descending and ascending. Useful in currents, poor visibility, darkness, etc. Also helpful to provide a
visual reference for inexperienced divers
datum to control the ascent and to provide a reference for staged
stops
datum for the surface cover. This aids safety because the boat
knows the area the divers are in and, if followed on the ascent, it
ensures that divers surface at a specific location hence minimising potential problems with boats above
can mark the precise location of a search datum or an object.
Consider situations where and when a shot-line should be used/might
not be used. Give practical examples/draw examples from students.
Why not use the boat’s anchor line ?
If the boat is anchored securely, the line angle does not provide the
shortest route between the surface and the bottom. While in some circumstances this may be an acceptable, it does not mark a precise
location.
For safety considerations the boat cover should usually be mobile, in
case divers need boat support, not a boat that is anchored.
VA Shot.5
Simple shot
Describe the parts. The line should be kept as short as possible to provide a near vertical descent/ascent. This will be more comfortable and
saves dive time. It will also ensure that the float on the surface is close
to being directly above the shot weight – so that the position of the
dive site is accurately marked on the surface.
VA Shot.6
The simple shot works well in situations where the depth of water is
accurately known and is not subject to tidal variation.
Top tensioned shot
This effectively works on the rope and pulley principle to adjust the
shot-line for water depth to overcome the limitations of the simple
shot. Its own limitations must, however, be understood. The line is not
attached to the buoy, but passes freely through a metal ring attached
to the buoy. The counter weight tensions the line.
VA Shot.7
© BSAC 2000
A top-tensioned shot-line does not cope well with tidal currents – the
drag on the buoy caused by the current can pull the counter weight
right up, so the line is not vertical. The two vertical elements of the line
can also tangle. The size of the counter-weight must be carefully chosen. Explain how the weight of the main shot will be effectively
reduced by this amount.
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Instructor Notes: Search and Recovery
Bottom tensioned shot
Describe its construction. It again uses the rope and pulley principle,
but using a small float to tension the line from the lower end. Point out
the need for the line to run smoothly through the shot weight by use
of an attached metal ring, karabiner or similar. This configuration has
similar limitations to the top-tensioned shot and the buoyancy of the
float will again reduce the weight of shot.
VA Shot.8
A lifting bag can be used instead of a float, but this requires work
underwater to tension the line. The bag can be partially filled (sufficient to tension the line) by the first pair of divers on descent, and then
fully filled by the last pair of divers to leave the site at the end of the
dive to assist shot recovery.
Use of a waster
A waster is a light line, attached to the main line before deployment,
which is used by the first pair of divers to tie the shot-line to the dive
site. Its strength is such that it is strong enough to secure the shot on
site during diving but can then be broken (‘wasted’) by pulling on the
shot-line from the surface after the dive, thus allowing the shot-line to
be recovered. It can be used with a weight or a grapnel.
VA Shot.9
Discuss with the class the dive marshalling implications of using such
a system:
choice and order of dive pairs
first pair of divers must take great care to avoid pulling the shot
weight off the dive site as they descend
● use of a signal float to be sent up to show that the remaining
pairs can dive, etc.
● last pair of divers to leave the site must ensure that the shot
weight or grapnel is free to be lifted. Alternatively it may be
unclipped from the shot-line and sent to the surface on a lifting
bag.
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Construction of a shot-line
Explain the characteristics common to all shot-line configurations:
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VA Shot.10
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weight – needs to be of an adequate size (approximately 25 kg)
to ensure it cannot be dragged off site by current or descending
divers. A grapnel can sometimes be used, to hook into wreckage.
buoy – adequate size. Preferably 50% more buoyancy than the
weight of the shot.
line – sufficient strength but also of a size that is easy to handle.
Quite thin line can be strong enough but use 15–20 mm for
greater comfort, less entanglement risk and ease of recovery.
line length – keep as short as practical. If the length of the line is
based on the depth to the wreck, not the seabed, then you can
tell when the shot has missed the wreck – it will be free to drift.
Extra line – can be ‘trailed’ on a small buoy. Chain senneting can
keep extra line tidy.
karabiners/clips – easier to use than knots. Suitable knots will be
shown in ‘Workshop’ Session.
© BSAC 2000
Instructor Notes: Search and Recovery
‘Tide’ or trailing buoy
These perform a number of functions:
observation of the current. By observing the pull on the ‘tide’
buoy, the strength of the current can be assessed to determine
when the current is slack enough to dive.
● in case main buoy pulled under by tide! This is a particular consideration in areas of strong tidal flows so that shot-lines can be
positioned in preparation for slack water.
● divers less likely to drift past the shot on entering the water. They
can grab the trailing line.
● can be used to keep extra line out of the way.
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VA Shot.11
Decompression stops
Where decompression diving is planned, a separate line can be
rigged to aid decompression stops. This is joined to the main shot-line
by a ‘travel line’, which is clipped to main line such that the clip is free
to run up and down the line. The decompression line may just have a
weighted end at the depth of the deepest decompression stop or may
have a decompression trapeze and/or spare gas for emergency use
on the stops.
VA Shot.12
Having a separate decompression line allows divers ascending from
the site to carry out decompression stops clear of the shot-line, which
may still be being used by other descending divers.
Where tidal windows dictate that decompression stops may have to
be performed after the end of slack water, the travel line can be
unclipped from the shot-line by the last pair of divers to return. This
allows decompression to be carried out drifting with the tide – which is
far more comfortable for the divers than having to hold position stops
on fixed shot in a current.
All divers must, however, get back to the shot and be back on the
decompression line before it is released. This requires a system of
markers which, on descent, the leader of each pair attaches to the
travel line near to the clip fastening it to the shot-line. On ascent the
leader of each pair removes one clip as the pair pass via the travel line
onto the decompression line. The diver removing the last clip then
knows that there are no divers remaining on site and the travel line
can be safely unclipped (once both divers are holding on to it!). Discuss the use of marker clips or a similar system, the implications on marshalling, dive discipline, etc.
Deployment and recovery
Deploying and recovering shot-lines requires care and a methodical
approach that allows for the effects of surface conditions, currents and
wind. The cox’n of the boat is in charge of the operation and should
tell the person deploying the shot when to let go. Explain possible
methods to keep the line free of tangles to prevent snagging on equipment – coil carefully, ‘flake’ into a bucket or similar container, etc.
VA Shot.13
Once deployed, the shot-line should be observed to check that it is
holding position and not drifting off the site. (Quiz the class for how this
would be done).
If the dive site is a regularly dived area then the shot could be left as
© BSAC 2000
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Instructor Notes: Search and Recovery
a semi permanent marker, saving much time and effort. The shot-line
would need to be fixed securely to the site (e.g. tied to wreckage) in
this case.
To recover the shot-line, divers should try to ensure that the weight is
not trapped on site prior to ascending. Power winch and/or pulley systems are available on some hard boats, but elsewhere the only
recourse is to manually haul up the shot-line. Decompression considerations make strenuous exercise immediately after deep diving
undesirable, so wherever possible the shot-line should be recovered
by a non-diving or shallow diving member of the party.
The last pair of divers to come back up the shot-line could attach a
small lifting bag to the weight and add a small amount of air to help
retrieval. (Or the first pair tie off the shot-line with a waster, then unclip
and send the shot weight up free).
VA Shot.14
Summary of the shot-line
Recap the main points of the lesson. In particular emphasise the ways
a shot-line can enhance dive safety.
This could be done by questioning the students to check they have
absorbed the information.
Example questions:
How does a shot-line increase diver safety?
How does a shot-line increase diver comfort?
What size weight should be used?
What size float should be used?
What diameter line should be used?
What length line should be used?
Use supplementary questions to draw out all the required information.
VA Search.1
SEARCH OPERATIONS
45 MINS
VA Search.2
Lesson introduction and contents
Briefly explain the topics that will be covered in this lesson and how
they will relate to the subsequent practical lessons.
Hazards of search and recovery diving
Briefly review the main hazards likely to be encountered and how they
can be minimised:
entanglement – this is a major problem when using lines of any
type. Carrying an effective knife is essential. Give advice on suitable knives, e.g. carry a sharp knife with a serrated edge for
heavy lines/line cutter for light lines. Show examples
● low visibility – the lower the visibility, the slower movement needs
to be to avoid entanglement, not just with lines, but also with any
unknown objects on the bottom. Lack of buoyancy control can
cause reduced visibility whilst conducting a search. Good buoyancy skills are required during search and recovery diving
● currents – discuss problems that currents can potentially cause.
Search upstream to lessen problems with visibility. Line
searches will prove difficult in currents and should be avoided.
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VA Search.3
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Instructor Notes: Search and Recovery
Other techniques could be used.
charts and tide-tables – when conducting searches in the sea,
use charts and tide-tables to determine the possible hazards
associated with the dive site and likely water movement
● usual safe diving practices still take precedence and should not
be ignored by divers concentrating/distracted by the task.
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Requirements for a successful search
Outline the requirements for conducting a successful search:
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VA Search.4
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the search should be kept as simple as possible. The less there
is to go wrong the less is likely to go wrong – otherwise Murphy’s
Law rules! It is also easier to train divers for the task
the search must be effective. Measure in terms of costs and the
effort involved. Is the lost object worth it? Is the experience
gained by the search party worth it?
100% coverage of the search area is essential. Until the object
of the search is found, it is just as essential to be sure that it is
not in the area already searched
navigation problems, both on the surface to set the area of the
search and underwater to carry out the search, need to be
reduced to a minimum. Effects of tide, currents and wind must all
be taken into account. Electronic navigation can be very effective
adaptability is essential. Divers need to be constantly aware of
their surroundings and adapt the dive/search plan accordingly.
Research stage
For a search and recovery operation to be successful the first stage of
planning is to identify exactly what is to be recovered and as much
information as possible about where it is.
what is being searched for? Will divers recognise it/find the right one?
what size is the object?
what is the object likely to weigh underwater (needed for lifting)
and how much does it weigh in air (needed for removing it from
the water)?
● what information is available about its position? How accurate is
that information likely to be?
● how much information is available about the time of loss and the
weather/tidal conditions at the time?
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VA Search.5
Given the above information, a best estimate of the position of the
object can be made. How well the position can be estimated, and
hence the search area limited, will depend on the level of confidence
in the above information.
Types of searches
Choice depends on:
size of the object – a larger object will not require as meticulous
a search so a larger area can be covered. Small objects will
require a more meticulous search over a small search area. A
small object within a large search area is possibly not worth it!
● the bottom topography – e.g. large boulders and kelp might be
best searched using a compass technique; most wrecks are
made of steel which might affect a compass
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VA Search.6
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Instructor Notes: Search and Recovery
visibility – the search technique needs to be matched to the
underwater visibility in the search area. The worse the visibility,
the smaller the area that can be scanned at any one time
● what equipment is available? Some searches require specific
equipment that may need to be obtained
● water movement – the method chosen will need to be practical
in the expected conditions.
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Grid search
The principle of a grid search is to divide the search area into a number of much smaller areas, the size of which is determined so that
each can be viewed in its entirety. The small areas are then searched
in sequence. Explain the characteristics of grid searches:
VA Search.7
good for searching for small objects
effective for small areas.
with an appropriate grid size 100% coverage of the area is possible.
need a substantial amount of equipment and good organisation.
The lower the visibility, and hence the finer the grid, the greater
the logistical and organisational aspects
●because of the precision and coverage, grid searches are often
used for surveys – marine biology, archaeology, wreck surveys, etc.
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Jackstay search
The jackstay search is an excellent method when looking for something small in a restricted area.
VA Search.8
A jackstay is a line fixed to the bottom by weights and used as a datum
line for searching. A jackstay may be fixed or moveable, dependant on
the search technique adopted. It may be deployed either by divers or
from a boat. Describe the search pattern around the jackstay. In its
simplest form, divers search to the limit of visibility along one side of
the line, around the weight at the far end, back along the other side
and finally around the other weight to return to their starting point.
Discuss various ways of deploying the equipment, depending on circumstances. Could be all deployed from a boat, or by divers from the
surface or underwater, or any combination.
Moveable jackstay
To cover a larger area, a single jackstay line can be moved across the
seabed. The distance that the end of the jackstay is moved is limited
by the extent of the underwater visibility or object size. By following a
logical sequence and ensuring a degree of overlap, 100% coverage
of the area can be ensured. No additional equipment is needed.
VA Search.9
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Instructor Notes: Search and Recovery
Jackstays for a grid search
Jackstays can be deployed in parallel lines on the seabed as baselines from which a grid can be laid.
VA Search.10
Parallel baselines plus moveable jackstay
This effectively involves three jackstays, two fixed as datum lines and
one moveable jackstay between the baselines, and at right angles to
them.
VA Search.11
The divers swim up one side of the movable jackstay and down the
other. The jackstay is then moved along a suitable distance (again
dependant upon visibility/size of the object) and the process is
repeated. A degree of overlap is included in the area searched each
time the jackstay is moved to ensure 100% coverage.
This results in a form of grid search pattern (where each element of
the grid is a long thin element stretching the full width between the
baselines). The searched area can be clearly defined.
Circular search
Describe the characteristics of a circular search:
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VA Search.12
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the basic principle is to search a series of ever increasing circular sweeps around a central datum point
an excellent search for locating small or large objects on a flat
bottom. Discuss the types of seabed this is suitable/unsuitable
for. Best on an unobstructed bottom – kelp and boulders will continually snag the line
because the area that can be covered is relatively small a reasonably accurate estimate of the lost object’s position is required
little equipment is required
as with other searches the distance between sweeps depends
upon the underwater visibility and size of the object
using an appropriate sweep size and overlap can ensure 100%
coverage
where a full circle is not possible (e.g. around a rock face, harbour wall, etc.) the technique can be modified to a pendulum or
semi-circular pattern, sweeping in alternate directions
Circular search practicalities
Describe the practicalities of carrying out a circular search:
use a heavy central shot weight, to prevent it being dragged
clearly mark the starting position so that complete revolutions
around the shot-line can be determined. A distinctive object
taken along specifically for this purpose can be used but a separate, fixed light bottom line is usually best for this, run out from
a separate weighted reel. This is less easy to miss in poor visibility than other types of marker
● use a reel with a light line as a swimline. Keep the swimline
taught. Secure the swimline in such a way that it will not ‘ride up’
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VA Search.13
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Instructor Notes: Search and Recovery
the shot-line and thus distort the search pattern
a practical maximum limit of sweep size is about 20 metres
once found the object can be marked by fastening off the swimline or by using an extra reel and delayed SMB carried for the
purpose
● for large objects on a flat unobstructed bottom the sweep line
can be used as a ‘snag’ line.
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Compass searches
A compass and a timing method can be used to swim a series of
headings which result in a square based pattern. The length and direction of each leg can be adjusted to result in ‘square spiral’ or ‘rectangular zig-zag’ patterns.
VA Search.14
Explain the characteristics of compass searches highlighting the possible advantages/disadvantages of a compass search. Discuss the
circumstances where it might be suitable (e.g. uneven sea bed):
very little equipment required
not suitable for finding very small objects
hard to control precisely and hence cannot ensure 100% coverage
whenever possible use the cardinal points of the compass (N, S
E, W) for simplicity.
● one person should navigate whilst the other looks for the object.
(monitor your buddy!).
● course can be plotted on a survey chart but will require a clearly
defined starting point.
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Compass search patterns
Briefly describe the conduct of the ‘square spiral’and ‘rectangular zig-zag’
patterns.
VA Search.15
Swimline searches
Swimline searches are used to cover very large areas and hence are
very demanding in terms of resources and competency.
Because of the distances involved, a light baseline, which can be
thousands of metres in length, is run out from a boat. This is done at
speed so that the line can be kept straight and tight and so that the
direction of the line can be more accurately controlled.
VA Search.16
The baseline is heavily weighted and is marked with a large buoy at
each end. Other smaller weights may be attached to the line at intervals. The position of the baseline is plotted on a chart.
If required, a series of parallel baselines can be laid out if a wide area
is to be searched.
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© BSAC 2000
Instructor Notes: Search and Recovery
Swimline searches
In order to cover a large area a team of many divers is used. Explain
how a swimline search is conducted underwater highlighting potential
problems (e.g. organisation, control, communication, equipment etc.):
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VA Search.17
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a swimline is used to link together a team of searching divers.
The swimline length depends on the number of divers and the
underwater visibility
the swimline controller is usually in the middle over the baseline,
with divers each side
the distance between the divers is determined by the underwater visibility, allowing for a suitable overlap
communication is by rope signals passed along the line
movement of the team is hard to control.
There are many variations on the swimline search method described
above.
Sonar/magnetometer searches
Briefly explain what sonar and a magnetometer are and hence what
they would show. Give examples of what each could be used to
search for.
VA Search.18
Unlike the previous search techniques described these are carried out
from boats on the surface, not by diving. They therefore provide a
quick coverage of a large area. They are, however, only useful for
searching for large objects.
Various search patterns are possible. Draw parallels with those
described for underwater searches, e.g. circular around an initially
deployed shot-line; or ‘lane’ pattern with or without deployed shotline(s) to help. The distance between ‘lanes’ is determined by the
width of the coverage of the sea bed provided by the equipment.
Accurate navigation is needed to ensure the area is 100% covered for
which GPS is ideal. Use of GPS plotter screens, which plot the course
followed and so show the area searched provide a useful means of
controlling the search pattern.
Making life easier
To minimise problems underwater, pre-prepare as much equipment as
possible. Ensure that the techniques to be used are fully practiced on
dry land beforehand.
Use suitable equipment; do not make do. Refer back to the lessons on
shot lines to highlight the type/size/quality of buoys, shot weights, line,
clips, etc., required.
VA Search.19
Minimise problems with stirred up silt by working into the current. To
ensure 100% coverage, a slight visual overlap is required between
search elements. On uneven sea beds remember to look behind
rocks!
Where boat access is not possible, a shot-line can be used as a means
of transporting equipment to the site. Attach tools, lines, lifting equipment
etc. to the line and allow them to sink to the weight. By doing this, all
equipment is to hand for the search team, and the buoyancy of the divers,
who would otherwise have to carry them to the work site, is not affected.
© BSAC 2000
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Instructor Notes: Search and Recovery
Ensure that the divers have a means of marking the object once it is
found.
VA Search.20
Summary
Recap the main points. Especially emphasise what is needed to
ensure a search is effective.
This could be by questioning the students to check they have
absorbed the information.
Example questions:
How might you know where to start your search?
How would you know what area to search?
What activities are required before the in-water search is started?
How do you decide what search method to use?
What factors influence the choice of search method? (Try to get
suggestions of the circumstances where each of the main types
of search might be used).
How much of the search area should be covered?
How would you know which areas have been searched?
Use supplementary questions to draw out all the information covered
in the Summary slide.
SHOT-LINE CONSTRUCTION WORKSHOP
60 MINS
This session should allow students to familiarise themselves with the
various items of equipment and to practice the construction of the various shot-line configurations. Demonstrate each aspect to the students, and then give them the opportunity to gain ‘hands on’ experience. Topics to cover should include:
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lines; buoys; shot weights of various types/sizes; anchors; grapnels
attachments – knots, clips. Joining lines and attaching lines to
buoys, weights, karabiners etc. Knots practiced should include
the sheet bend, bowline, round turn & two half-hitches, cow
hitch, fisherman’s bend, etc. Show finished examples of spliced
eyes and joints
shortening lines – chain senneting
attachment to an anchor/grapnel to allow it to ‘break out’
rope handling – containers for shot-lines, coiling, flaking line, etc.
construct shot-lines of different configurations for a variety of
given depths:
— simple shot
— top-tensioned; bottom tensioned
— deco line – with/without spare cylinder(s)
— shot(s) with tide buoy
attachment of waster line before deployment
attachment of lift bag before deployment, to reduce need for
underwater work.
SEARCH TECHNIQUES: DRY PRACTICE 1
30 MINS
Instructors should demonstrate each procedure, then give the students time to practice. Monitor and coach them at this stage.
The dry practices should mimic as closely as possible the in-water
searches to be done later, including a dry run of equipment deployment/recovery, roles to be undertaken by each individual, etc.
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Instructor Notes: Search and Recovery
Emphasise the value of dry practice when organising real underwater
work, and especially the value of mimicking the in-water process. It
means there will be much less confusion underwater where communication is more difficult.
Cover two types of search in this session:
compass searches. Pick a simple search pattern, suitable for the
venue used
● circular searches. The instructor demonstrates deploying the
shot-line, distance line and sweep line.
●
SEARCH TECHNIQUES: DIVE 1
100 MINS
Ideally use an area about 6 metres deep with a fairly flat, clear bottom.
Remember that these techniques will have been rehearsed in the dryrun session and that that practice should be built on.
The instructor demonstrates a compass search. Use a fairly simple pattern and small search area. Students then practice the
technique
● The instructor guides the students through the circular search
techniques previously practiced. It should not be assumed that
the students will remember everything and hence the instructor
must actively direct the actions that the students are to take so
that they successfully implement the technique. (Note: actually
finding an object is not necessary for success, this is an instructional exercise not a real search.)
●
SEARCH TECHNIQUES: DRY PRACTICE 2
30 MINS
On a full day event this, along with a break, forms a surface interval
between dives.
This lesson should follow the same format as the previous dry practice session but covering deploying a jackstay and conducting a
jackstay search. Ensure that the students fully rehearse the in-water
activities.
SEARCH TECHNIQUES: DIVE 2
100 MINS
Instructor works with students to deploy the equipment for a jackstay
search. This time the students should take most of the responsibility
for organising and controlling the deployment (Note: the process for
deploying one shot-line will have been taught in the circular search
exercise). The instructor should coach them through the process and
ensure it is safe. The instructor then demonstrates this search technique. Cover a method of moving the jackstay after completing one
‘pass’. The students should then be guided through the practice
search including moving the jackstay.
RECOVERY OPERATIONS
VA Rec.2
© BSAC 2000
45 MINS
Outline
Outline the topics that are going to be covered in the lesson and how
they will relate to the subsequent practical lesson.
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Instructor Notes: Search and Recovery
Buoyancy for lifting
As much of the information regarding buoyancy will already be known
to the students from their diver training, use this to recap this knowledge by drawing the information from them by questioning. Ensure
that the following are fully understood and where necessary provide
appropriate explanations:
●
VA Rec.3
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how displacing the water in a container with air will result in positive buoyancy that can be used to lift objects
the relationship between the volume of water, its weight and the
buoyancy it provides
Boyle’s law and its relevance to the amount of free air required
at the operating depth
the consequences of the expansion of the air during the ascent
with the attendant increase in buoyancy, and hence speed of
ascent
the need to ensure that the expanding air can be freely vented
Weight of object
Knowledge of the weight of the object to be recovered is the essential
starting point from which the capacity of the necessary lifting bags and
the volume of air needed to inflate them is determined. There are
many methods of estimating or finding out an objects weight – including weighing a similar item, reference to manufacturer's manuals,
specifications, etc.
VA Rec.4
Ensure the students understand that the water displaced by the object
itself will result in an up-thrust and that therefore its weight will be less
when submerged in water. While this will result in a reduction in the
buoyancy required to lift the object to the surface, the full weight of the
object will still need to be borne when it is removed from the water.
Work through the process of calculating the object's weight using the
simple example of a concrete mooring block.
VA Rec.5
Continue the example with the determination of the block’s weight in
water and hence the buoyancy required to lift it.
Use more examples, if necessary, to ensure the students fully understand the concept and process.
VA Rec.6
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Instructor Notes: Search and Recovery
Lifting bags
A variety of types and sizes are available – from a few kilograms for a
divers personal lifting bag to those capable of lifting several tonnes
when used on commercial salvage operations.
Other containers can also be used provided that they are air-tight, have
the necessary strength and can be securely attached to the object to
be lifted, e.g. oil drums, a dive bag with a bin-liner inside, etc.
VA Rec.7
Show examples of lift bags. Describe the rationale for their shape – to
reduce the risk of air spillage on ascent and give stability on the surface. Some bags may have valves to control deflation. Selecting the
right size for the job is important. Too small and the object will not be
lifted; too large risks a rapid and uncontrolled lift.
Attaching lifting bags
Lifting bags should be attached to the object using attachment points
that are strong enough. They must also provide security to prevent
any attachments slipping off.
VA Rec.8
Attach the lifting bag(s) using simple methods that can be pre-prepared on dry land. Wherever possible avoid having to tie knots underwater. Karabiners/shackles provide a far more manageable and effective solution. Show examples and discuss their relative merits.
Larger objects may require wire/webbing/rope strops to achieve a balanced lift. Delicate items, or objects whose shape provides no adequate attachment points, will need to be lifted using trays/bags etc.
Do not forget that any equipment used needs to be transported down to
the lift site. Carrying heavy equipment will have a significant effect on
personal buoyancy. An easier method is to slide the equipment down a
messenger line to the work site – ensuring that all divers are clear!
Depending on the size and shape of the object a more stable lift may
be achieved by using a number of smaller lifting bags rather than one
large one.
Multiple lift bags
Using several smaller bags, rather than one larger one, gives a
greater degree of control.
For example, for an object needing 150 kg of lift (i.e. litres of air):
VA Rec.9
One large bag will be very difficult to control once it is fully inflated.
Three 50-kg bags will provide the same lift and can be inflated independently. With two fully inflated, the third can be used to control the
lift. A dump valve would allow fine-tuning of the ascent rate. Three
bags will also allow a more balanced lift.
Where the capacity of the bags exceeds the lift required, arrange the
bags so that all but one are full before the lift starts. The final bag
should be the smallest available in excess of the required lift. As the
ascent progresses, the expanding air will vent from the full bags
whose buoyancy will remain constant. Only the final small bag’s buoyancy will increase during the ascent before it also vents excess air.
Limiting the size of the final ‘control’ bag also limits the excess buoyancy that can be generated and hence the ascent rate.
© BSAC 2000
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Instructor Notes: Search and Recovery
Air requirements
Review the air requirements calculation method. Refer back to the
calculation of the weight of the object in water and hence the buoyancy required. 1 litre of water weighs 1 kilogram irrespective of depth,
but the amount of air required to displace this amount of water
increases in relationship to the absolute pressure (depth).
VA Rec.10
If intending to fill a lifting bag from the diver’s air supply it is vital to work
out the air requirement for the dive and the air requirement to lift the
object. This will determine the size of cylinders required and, depending on the answer, may dictate that dedicated cylinders are used to fill
the lifting bag unless very little air is needed for this purpose.
Discuss with the class the various options for filling lifting bags:
on no account use primary regulator!
AAS/octopus – limited to small lifting bags; consequences of
trapping a 2nd stage in the mouth of a bag/attachment webbing
/strops as it fills; ways to avoid this; beware of ‘free-flow’
● air gun – more controllable; requires dedicated air hose so probably also a dedicated air supply; less likely to become trapped;
less likely to free flow
● separate cylinder(s) – essential for large objects; advisable for
small objects unless certain the diver’s own air supply is adequate for both the dive and the lift; surface supply air can sometimes be used although this is not normally available to amateur
divers.
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The lift
Once the lifting bags have been attached to the object they should be
inflated with a small amount of air and, once floating in the lifting position, their security should be checked. All except the ‘control’ bag
should then be filled evenly and the ‘control’ bag carefully topped up
until the object starts to rise.
VA Rec.11
The object might need extra buoyancy to ‘break out’ of the seabed –
this might result in a sudden, fast ascent. It might be possible to lever
the object partially free or move it or shake it, to break the suction.
Discuss the potential dangers while carrying out the lift, and possible
means of avoiding them:
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careful planning – air requirements, depth, times, etc.
use of a ‘dry run’ and/or practice in shallow, safe water
never ride up on the lift
move clear from under the ascending object.
Once the object is on the surface, check the security of the lifting bags
again and, if any air has been spilled as the bags broke the surface (a
problem with rapid ascent rates), top up the lifting bags. Recovering
the object into a boat will require a means that is capable of accommodating both the size and the whole weight (in air) of the object.
If the object is to be towed by the boat, top up the lifting bags at the
surface and check their security before the tow commences. Adjust
the speed of the tow so that the bags remain in a stable attitude.
Reduce the towing speed immediately any instability is noted. Check
the security of the bags and top them up regularly during the tow. Be
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Instructor Notes: Search and Recovery
ready to abandon/cut the tow if the bags deflate and the object sinks.
Staged lift
A staged lift provides a more controlled ascent rate which may be
essential for delicate objects and also allows most of the work to be
done in shallow water.
VA Rec.12
The object is secured to a line which has pre-prepared loops at intervals along its length. Two lifting bags are then used at the surface end
of the line, each of which is capable of lifting the object. As each bag
reaches the surface, the other is moved to the next lower loop. The lift
therefore proceeds as a series of small increments as each bag is
repositioned in turn.
With the excess lift available from the two bags, objects can be ‘broken out‘ of the sea bed. As both bags will be inflated close to the surface any subsequent rise will be restricted, thus preventing a rapid
ascent.
Discuss with the class how the line may be run to the object from the
surface initially.
From the surface:
deploy the pre-tied line as a shot, complete with weight and
buoy. Divers then take the shot weight (and hence the line) to the
object
● swim one end down to the object. A shot-line to follow will be
needed directly to the object
● weight the end of the line and attach it by a suitable karabiner so
that slides it down a messenger line or shot line.
●
From the sea bed:
take the whole line to the object, coiled, ‘stuffed’ into a bag (better), or wrapped on a drum or reel. Once attached the free end
is returned to the surface using a DSMB or similar method
● divers surface, bringing up the free end with them.
●
Legal aspects of lifting material from wrecks
Note: For courses run outside the UK, instructors should substitute the
appropriate local legal requirements for this and the subsequent slide.
VA Rec.13
All wrecks belong to someone. The wreck itself, cargo and personal
effects might in fact have different owners. With certain exceptions,
recovering objects from them is not illegal in itself, but keeping the
objects without giving the rightful owners the opportunity to claim their
property is theft.
It is a legal requirement that all recovered wreck is reported to the
Receiver of Wreck, who is responsible for the administration of part of
the Merchant Shipping Act 1995. Recovered items must be reported,
even if you own the wreck. There is no obligation to report anything
not recovered. Wreck needs to be reported to give the legitimate
owner the opportunity of recovering their property.
Some wrecked ships and aircraft may be military remains and should
be treated with the appropriate respect. (Note: strictly, the term ‘war
© BSAC 2000
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Instructor Notes: Search and Recovery
grave’ only applies to land cemeteries. Military vessels lost on active
service are technically known as ‘derelicts’ but should nonetheless be
treated as the marine equivalent of a war grave.) Most military vessels
may be dived, but not disturbed or entered. Under no circumstances
may material be removed from them. Certain sites in exclusion zones
may not be dived at all. Salvage of military ships or aircraft needs the
specific, prior approval from the Ministry of Defence.
Refer students to the contact details that are given in the Student
Notes, and to the Wreck Divers Code of Practice included in the Student Pack.
Legal Aspects of Lifting Material from Wrecks
Old wrecks have additional considerations because of the valuable
historical information that they can provide. If you suspect you have
found an old (100+ years old) ‘unknown’ wreck, mark the position
accurately; don’t talk about it (especially to other divers!) and report it
to the relevant authorities:
VA Rec.14
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around England – the Department of Culture, Media and Sport
around Scotland – Historic Scotland
around Wales – CADW
around Northern Ireland – the Department of the Environment.
Do not disturb anything on the site as you will possible be destroying
valuable information by doing so. Almost all material will quickly deteriorate after immersion in salt water once returned to air. Objects are
often best left in a stable condition on the seabed.
The appropriate experts will investigate reports of such sites and, if
deemed to be historically valuable, the site can be given protected status. It is possible to apply for a licence to dive an historic protected
wreck site, for further details of how to go about this see the Archaeological Diving Unit’s Web site.
Even if not considered for protected status, any activities on the site
should still be carried out in a way that preserves the historical value
of the site and any items recovered. The Nautical Archaeological Society can provide advice, assistance and training in how to do this.
In the UK, if any payment is received for diving, other than for genuine
and proven expenses, it is classed as commercial diving. This places
the divers under the regulation of the Health and Safety Executive and
full compliance with their diving regulations and procedures will be
necessary. Recovering objects and selling them for profit is a form of
payment and hence counts as commercial diving. Again refer students to the contact details that are given in the Student Notes, and to
the Wreck Divers Code of Practice included in the Student Pack.
VA Rec.15
Summary
Recap the main points. Especially emphasise what is needed to
ensure a lifting exercise is safe. This could done be by questioning the
students to check that they have absorbed the information.
Example questions:
Why do you need to know the weight of the object to be lifted? How
might you find its weight?
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Instructor Notes: Search and Recovery
How would you calculate its weight in water?
How big a lift bag would be used? Why might several smaller bags
be better?
Describe a lift bag. What are some common features?
How would you fill with air? What do you need to consider?
How would you attach lift bag(s)? What do you need to consider?
What safety precautions are necessary as the object ascends?
Use supplementary questions to draw out all the required information.
RECOVERY TECHNIQUES: DRY PRACTICAL
Working in groups with their instructor, students should become familiar with the equipment that they will use during the subsequent dives.
The instructor should demonstrate each element and then coach the
students through their practice.
Elements in the dry practice should include:
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measuring objects
determining the object’s weight and the lifting bag requirements
determining the best attachment method and lifting technique
determining the equipment required
inspecting lifting equipment
using slings and clips rather than knots and ropes
preparing the equipment for using inflation cylinders
dry runs of inflation techniques for small (AAS or octopus inflation) and large (dedicated air cylinder inflation) lifting bags
SEARCH AND RECOVERY: DIVE 1
Ideally use an area up to about 6–10 metres deep.
The students should work in their groups, with the Instructor demonstrating appropriate aspects and then coaching the student through
their practice. The logistics of this session can be eased if the equipment is set up as a series of stations that the students move between.
The dive should involve a progression through the following exercises:
a simple lift using a 5-litre container attached to a belt with
weights (ideally 5 or 6 × 1 kg), to demonstrate weight and volume
of air relationships
● lifting an object of about 25 kg, under control, using a weight on
an attached line to act as a break. Returning the object to the
seabed under control
● a staged lift of an object of about 25 kg.
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The above should include practice in:
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attaching lifting bags to the objects
use of a dedicated air source
SEARCH AND RECOVERY: DIVE 2
Set up a search and recovery exercise for an object of more than 30
kg using multiple lifting bags. For this exercise the students, working
in their groups, should take most of the responsibility for organising
and controlling the search and recovery stages. Two groups should
work together with one taking responsibility for the search and one for
the recovery. Instructors should ensure that the necessary co-ordination between the groups takes place and is effective. The instructors
© BSAC 2000
21
Instructor Notes: Search and Recovery
should coach the groups throughout the process (this is a learning
exercise not a test) and ensure it is safe. Ensure that all the following
aspects are fully addressed by the students in their planning:
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locating the object to be lifted
attaching the lifting bags
inflating the bags under control
securing the object at the surface
bringing the object ashore
recovering equipment and clearing the site.
COURSE DEBRIEF AND OPEN FORUM
22
30 MINS
© BSAC 2000