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COLD WATER SCUBA DIVING
SEARCH AND RECOVERY OPERATIONS
Chuck Lewis
SARRCOInc.
515 116th Avenue N. E., Suite 101
Bellevue, WASHINGTON 98004 USA
SCUBA diving search and recovery operations are difficult
under the best of circumstances if only due to the limited
vision afforded a diver by the required facemask. Cold
water search and recovery operations include the
additional obstacles of the increased drag produced by a
diver's thermal protection, reduced surface light,
frequently reduced visibility, and extreme surface and
subsurface environmental conditions. To overcome these
problems and conduct safe and successful search
operations in cold water requires training, equipment and
techniques that divers confronted with this type of an
assignment frequently do not have.
INTRODUCTION
All SCUBA divers conduct searches. In fact, every time a dive
on SCUBA is made it is for the purpose of searching for something.
The urgency of these searches is dependent upon the object of the
search and the vocation of the divers involved. A sport diver would
love to find a rock formation thickly populated with abalone, while a
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manne biologist may need to find that same formation for the
purpose of scientific research. The difference is that the biologist is
probably operating under the contstraints of time and funds. As the
priority of the search increases, so does the need for the
aforementioned specialized training, equipment, and techniques. If
the search is to be conducted in cold water, then the need for these
items increases dramatically.
COLD WATER SEARCHES
Cold water searches are rendered problematic for a specific
number of reasons:
1.
Reduced visibility due to plankton blooms, disturbed water
(caused by currents, storms), glacial deposits, and the reduced
surface light that is common to the colder climes.
2.
Increased air consumption due to poor thermal protection.
3.
Reduced bottom time due to poor thermal protection.
4.
The increased swimming effort required as a result of the drag
produced by the bulk of the thermal protection diving suit.
5.
The increased potential for decompression sickness on deeper
dives.
For these reasons, a diver responsible for search operations will
want to use methods which will maximize the area searched,
minimize the bottom time and thus reduce the time spent searching
and increase the time available for work projects.
PROCEDURES
The first step in the search process is to assess the problem.
The object of the search must be identified, the area to be searched
must be located and categorized, and the environmental conditions
must be evaluated. The object of a search along with the
environmental conditions will dictate the specific equipment and
techniques used. For example, a weight belt recently dropped in the
shallow protected waters of a small bay will require a much different
effort than the need to locate the anchor of a missing marker buoy
last seen months ago in the deep water of a channel in which
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LEWIS. Cold Water Search & Recovery
currents are a problem. The urgency
account. Divers might consider taking
searching for the missing weight belt.
fallen overboard and disappeared, a
appropriate.
factor must also be taken into
lunch and warming up prior to
However, if the ship's cook has
little haste would be deemed
Step two is to organize. The first phase of organization requires
the collection and analysis of available information. The information
obtained is related to the area of the search and the available
resources. The best information relative to a search area naturally
will come from an eyewitness (e.g., "I saw it sink over there ...").
When an eyewitness is available it is valuable to put a surface
swimmer in the water and let the witness direct him to the
appropriate location and then mark the spot with a buoy. It is
difficult for most people to identify locations on the surface of a body
of water without a physical reference. A swimmer provides a
surprisingly efficient reference. Frequently, information regarding a
search area comes from a third party or is even hearsay ("The legend
says they dropped the treasure four rods north of that reef'). In
situations such as this it will be necessary to mark the area or areas
to be searched with a series of buoys. Even experienced divers can
become disoriented when using natural references over the surface
of a body of water. The second phase of organization is to inventory
the available resources. These resources will consist of equipment
and personnel and these factors could have a major impact on the
technique used.
SEARCH EQUIPMENT
A discussion of search equipment is appropriate here. While
underwater search equipment can consist of items such as high-tech,
deep diving, remotely controlled robots, it most often consists of
lines, harnesses and buoys. In areas of limited visibility, it is difficult
for a diver to maintain a proper search pattern and two divers are
more of a hazard to one another than they are a safety factor. It is
for these reasons that lines and harne·sses are used under these
conditions. A solo diver is tethered by a line to a harness worn over
his dry suit. A tender on the surface controls the line and the search
pattern and communicates to the diver through line pulls. A safety
diver remains at the water's edge, fully equipped and ready to
descend should the need arise. The lines used in this type of search
are most generally 1/4 in. braided polypropylene. Braided
polypropylene floats, is visible, and will not tangle. The most efficient
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method to store polypropylene search lines is to thread a section of a
specific length (50 or 100 ft.) into a drawstring mesh bag, allowing
the line to coil naturally inside the bag. The line will feed from the
bag smoothly and without kinks. A marine carabiner serves as the
attachment device for linking the line to the harness, providing a
locking system that is easily connected and disconnected but only by
deliberate action and not by accidental contact. The harness itself is
similar to a seat harness used for climbing and rappelling but it
should be stitched with nylon rather than cotton thread in order to
prevent rotting and separation.
For searches of large, open areas, towed sleds are
recommended. Many different designs have been constructed and
tested but almost all have one feature in common that is considered
by some professionals to be a serious flaw. The sleds are separate,
permitting the search divers to move out of the range of visibility
and therefore communication with one another. The SARRPlane
however (Fig. 1), keeps the divers within touching distance of one
another and the individual moveable wings permit a high degree of
maneuverability necessary for clearing underwater obstacles (Fig. 2)
that appear suddenly under low visibility conditions.
Fi2ure 1
When the search object is located, the divers simply disconnect
the SARRPlane and release it. The wings float to the surface and the
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LEWIS. Cold Water Search & Recovery
towing craft operator, experiencing- a sudden reduction in drag,
knows that the divers have "punched out". The searchers are then
free to mark the object or recover it. The SARRPlane permits large
area coverage and places the burden of maintaining a proper pattern
on the boat operator who has much better orientation guides to work
with than the search divers.
Figure 2
THERMAL PROTECTION SUITS
No discussion of cold water diving equipment, for search and
recovery or any other purpose, would be complete without some
reference to thermal protection suits. Out of NASA's space program
came the watertight zipper. It didn't take a rocket scientist to figure
out that if a system could be provided for keeping the water out of a
diving suit at the neck, wrists, and feet, this zipper would permit
~ntry into what would be a dry suit .for SCUBA divers. It wasn't long
before numerous designs flooded the market. Originally, the
neoprene suit was the suit of choice but in recent years the shell suit
has become state-of-the-art. The neoprene suits of times past were
either so bulky as to add tremendous drag to a swimming diver, or
they were so form fitting that when the diver pulled the suit on time
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after time, the tension on the seams caused them to part and they
soon became "wet" dry suits. While the shell suit provides no
inherent floatation or thermal protection, it does provide a low drag,
watertight covering. The diver's floatation and insulation are
provided by the garments worn underneath the shell.
Viking, D.D.I. and a.s. Systems all have different approaches to
thermal insulation. The Viking undergarment is a one piece, quilted
coverall with attached socks and is constructed of open-celled foam.
D.D.I. also uses a one piece undergarment made of Thinsulate, an
excellent insulator. The a.s. Systems approach is to layer the
undergarments. Their thermal set consists of a one piece long john, a
3/4 length sweat shirt, and knee-length shorts, all constructed of
Arctic Fleece. This system permits a diver to dress for existing
conditions and the Arctic Fleece, like the Thinsulate of the D.D.I.
system, wicks water away from the body and dries rapidly. The
outer shells of each of these suits differ signifigantly. The Viking
shell has its waterproof butyl rubber layer on the outside over a
heavy cloth fabric. D.D.I. places their waterproofing between two
layers of nylon and a.s. Systems impregnates their 420 denier nylon
pack cloth with a polyurethane coating. All of these shell suits have
numerous advantages over the neoprene suits of old, the most
prominent being their ability to maintain their watertight integrity
over long periods of use, the ease with which they can be donned,
and the more effective thermal insulation provided by their
undergarments. Cold water searches are frequently long, tedious
operations and the selection of a dry diving suit should thus remain a
priority among divers involved in this type of operation.
SEARCH PATTERNS AND METHODS
D nderwater search techniques consist of three different
patterns and two different methods. The patterns used are the arc,
circle and grid and the methods used are the line and towed sled.
The towed sled is used most commonly with the grid pattern but the
line method can be used with all of the aforementioned patterns.
Line searches in limited visibility areas are most efficiently
used with one tethered diver down, and a safety diver and tender on
the beach or in a boat. The search diver attaches the search line to
his harness at the waist by means of a carabiner. This provides a
secure, central attachment point and permits the diver to release the
line if necessary without losing it. Tender and diver communicate via
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line pulls, for example:
Two pulls-tender to diver...Stop!
Change direction!
Three pulls-diver to tender.. .I've found it!
Three pulls-tender to diver...Surface!
Four or more pulls-diver to tender...Help!!!
The safety diver remains at the water's edge fully suited up
and ready to enter the water if a problem develops. The search diver
must keep tension against the search line at all times. The tender
permits the search diver to swim in an arc until one sweep of the
area has been completed. He then signals the diver to change
direction and pays out as much additional line as there is existing
visibility (Fig. 3).
Fi~ure
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TENDER
SAFETY DIVER
This procedure is repeated until the object is found or the area
has been covered. The arc search can be used from the shoreline of a
rake, river or saltwater beach, or even from the deck of a boat. When
used in a river with a significant current, the diver swims out from
the shore downstream from the tender and returns in a pendulumlike pattern. Additional line is not paid out by the tender until the
diver has returned to shore and verbally advised that the search
path was clear, or that downstream obstacles are present that need
to be dealt with.
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The circle pattern is simply a modified arc pattern. However, it
can be used with a solo tethered diver and a tender only when the
tender is on the deck of a small boat or at the entry hole during an
ice diving operation. Most often the circle pattern is used with two
divers down, one of whom is acting as the tender/pivot point. The
pivot diver meters out the search line and marks a point on the
bottom. The search diver then swims in a complete circle until he
brings the search line over the reference point marked by the pivat
diver (Fig. 4). The pivot diver releases more line and the procedure is
repeated.
Figure 4
Grid searches can be used either with two divers sWImmmg, or
two divers on towed sleds. For situations where the search area is
limited, the bottom relatively even, the visibility poor, and the
search object small, a jaL:kstay pattern can be used with two
swimming divers. Proper pattern set-up is crucial for this technique
to be effective. Two parallel lines buoyed at each end are placed on
the bottom. The distance they are placed from each other will
determine the length of the search sweep as the purpose of these
lines is to designate the beginning and end of each sweep. For this
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reason, sinking, rather than floating line should be used. A third line
with clips on either end (battery jumper cable clamps work well) is
placed perpendicular to the two buoyed lines. Search divers begin at
one end and swim until they reach the opposite line. The ,search line
is then moved along the pattern line as far as visibility will permit
and secured there. The divers then follow the line diagonally back to
the other pattern line and repeat the process (Fig. 5). This is a time
consuming and equipment intensive system but as the diagram
shows, it provides nearly double the coverage of an area.
Figure 5
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The grid pattern used in conjunction with two divers on the
SARRPlane is much simpler, but can only be used in large open areas.
In addition, the search object must be of a sufficient size that two
divers traveling at 2-3 knots could expect to see it. For this system,
buoys are placed in a pattern that provides a slalom course for the
boat operator. The towing craft then runs down each slalom channel,
the operator taking care to insure that he has pulled the S ARRPlane
clear of the buoy line before making his turn (Fig. 6). This is the most
efficient method of searching large areas but for safety pnrposes the
available visibility should be no less than 10 ft.
RECOMMENDATIONS
A search effort in any body of water should not be taken
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lightly. In cold water with limited visibility, the dangers confronted
are increased by geometric proportions. Limited visibility may
hinder a diver from locating a lost object but a more important
consideration is that it prevents him from seeing obstacles which
may result in entanglement. Improperly insulated, a diver immersed
in cold water will experience a reduction of his ability to perceive,
decide, and react and as the symptoms of hypothermia become more
pronounced, his motor functions will be seriously affected. It must be
remembered by all cold water divers that hypothermia is the general
cooling of the body and since the body begins losing heat
immediately upon immersion, hypothermia may begin to set in
immediately upon immersion. The degree to which the symptoms
will be experienced and the time period in which they will be
experienced is dependent upon the rate of heat loss and/or the time
of exposure.
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This physiological fact was one of the major considerations in the
development of cold water search methods since inefficient area
coverage can lead to prolonged exposure time and result in an
increased rate of heat loss. Further, in many instances potential
bottom time is reduced due to increased air consumption, the
probable onset of the more serious stages of hypothermia and the
increased possibility of decompression sickness.
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LEWIS. Cold Water Search & Recovery
t
The search practices tested and ultimately adopted were found
to permit rapid, safe and efficient area coverage. Used in combination
with up-to-date thermal protection suits and careful mission preplanning these methods will help to insure a safe and successful
conclusion to any cold water search operation, regardless of priority.
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