Freediving
What is Technical
Freediving?
By Kirk Krack
Photo: Joakim Hjelm
I
n August 1998, I sat on the back
of the boat with Tanya Streeter
recapping our most recent training
session in preparation for her world
record, no-limits freedive to 370
feet (113m). I grabbed a tank of 80%
O2 decompression gas to ‘catch my
breath and off-gas’ from all the work
I had just done safety freediving.
Ten minutes later it was time
for me to check on two trimix
divers who were still underwater
decompressing at 15fsw (4.6msw). I
quickly donned mask and snorkel,
took one last breath and jumped
overboard and headed down to
them. I was a trimix instructor
trainer at the time, and I knew this
use of oxygen wasn’t a risk at this
depth for what was supposed to be
a quick chat. I joined them and we
had a quick hand-signal discussion
on their status, decompression
obligation, tank pressures and how
they were feeling. I then engaged
them on what they saw on Tanya’s
last dive via slate and pencil: her
decent, her bottom turn, her ascent,
the current and drift on the line,
safety procedures, etc. Soon one of
them stopped the conversation and
was staring at me blankly with their
36% O2 regulator in hand, offering
it up to me. The diver grabbed my
wrist and showed me my freedive
computer indicated I had been
down over 5 minutes on a single
breath. But I didn’t yet feel the need
to breathe! “Ping!” went the bell in
my head; I signaled the diver and
headed to the surface.
Thus began my enquiry into
what I have come to call ‘Technical
Freediving’, the use during breathhold diving of enriched oxygen
mixtures, including oxygen, as
a surface breathing gas to help
flush nitrogen and increase the
availability of oxygen to the tissues.
Used both before and/or after a
freedive, enriched O2 mixtures
(most commonly 32% and 36%)
can reduce fatigue, decompression
stress and surface intervals while
both increasing breath-hold times
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Magazine
and speeding recovery. Low
percentages are generally used
before freedives or high mixtures are
used after. Low before to increase
available O2 to the tissues and
high after to flush nitrogen and
aid recover. I have, in some of the
‘technical of technical freedives’,
used both combinations.
Fast-forward 18 years and
the enquiry that arose out of
happenstance has me researching
and developing protocols for safe
and effective Technical Freediving,
for use by deep safety in elite
freediving competitions to award
winning underwater cinematography,
to scientific research applications,
to the aging freediver or the
physiologically compromised or
maybe just the techie enthusiast.
Safety freedivers
at the Deja
Blue annual
competition use
enriched air to
relieve fatigue
during long days
with lots of deep
breathold dives
The diver grabbed my wrist and showed
me my freedive computer indicated
I had been down over 5 minutes
What are the advantages?
So why would you do something
that incurs a cost (gas), forces you
to swim something around (tank and
regulator) and disrupts the calm,
silent, serenity you enjoy during
your surface breathe-up (bubbles)?
Frankly, of all the advantages it can
provide, the most obvious one is
from my story with Tanya:
Bottom time: the holy grail for
every freediver is to gain a more
comfortable and safer extended time
at depth. In 2008, live on The Oprah
Winfrey Show, I trained magician
David Blaine to hold his breath
submerged in a 8ft (2.4m) diameter
glass sphere for 17:04 and a new
Guinness World Record all after
pre-breathing on 100% O2. In fact in
the Cayman Islands training the prior
week we did just over 24min. For
the everyday freediver a noticeable
difference in time can be achieved
using simple nitrox mixtures but
there are trade offs and adaptations
to safety that must be considered
beyond what is taught in simple
freediving programs.
Controlling fatigue & speedier
recovery in the working freediver
who needs to be there, day in
and day out, for 4-5 hrs at a time,
this can be the magic bullet.
Hyperbaric O2 therapy is used
extensively to accelerate wound
healing and so too does it assist
the recovering freediver.
Two years ago I was on a movie
shoot that had both actors and
camera operators doing over 100
freedives in the 50-100ft (15-30m)
range with average underwater times
of 1:30- 2:45. We would have been
exhausted after the first day and likely
working at a decreased capacity the
next. While we had three days of this,
we’re able to stay awake till midnight
prepping and at it again at 6am. We
achieved this on a modest mix of
36%, which can typically be ‘on-tap’
at most dive stores that sell nitrox.
Decompression stress differs
from fatigue in that it’s the work
of elimination of residual nitrogen
bubbles on the physiological system
that is fatiguing and not just a lack
of oxygen to recover. How many
scuba divers reading this remember
that day of diving when you were
just exhausted and staying awake
during dinner on the liveaboard was
near impossible? Freedivers can feel
these effects as well but they are
typically less pronounced.
Decompression illness is
something freedivers can also
experience, much like the scuba
diver who is symptomatic with
skeletal/muscular or neurological
deficits due to dissolved nitrogen.
It’s more unusual, but for the
experienced or professional freediver
it can happen if we don’t watch our
recommended surface interval and
break protocols. In April of 1999, I
experienced a Type II hit that left me
unconscious for 18 min. However,
upon reaching the chamber all
symptoms had resolved because
of the fast tissues affected and the
reduced ‘load’. Now, to be fair, back
then we didn’t know about surface
intervals and scooter freediving can
allow successive deep freedives
with hardly any surface interval at
all. That experience is the reason
we now have them. I also know of
a spearfisherman who needs to
drag around a bottle of O2 between
freedives just to avoid DCI on
freedives that others wouldn’t.
Reduced surface intervals/
increased bottom time, just as for
scuba diving, nitrox can help the
recreational or working freediver.
A 100ft (30m) 1:20 freedive might
require a mandatory 8min surface
interval, but if using a 36% nitrox,
the adjusted air depth equivalent
would be 75ft (23m), meaning the
freediver may increase bottom time
or decrease their surface interval.
be immediate and severe. Even
worse, at 27ft (8m) with 1.82ata
PP02, full exposure would be
achieved in 1min!!!
Also for the freediver, the natural
accumulation of CO2 during the
freedive is a pre-disposing factor
to oxygen toxicity, so that also
could affect them. However, oxygen
concentration within the lungs is
also dropping, therefore PPO2 drops
while exposure time increases.
What are the disadvantages?
Oxygen toxicity is the big
elephant in the room so let’s discuss
it first. As any trained nitrox/technical
scuba diver knows very well, high
partial pressures of oxygen (PPO2)
for too long can affect the central
nervous system with convulsions,
visual/hearing disturbances, nausea,
twitching, irritability and dizziness
(CONVENTID). The convulsions are
the most life threatening. But this just
means a Technical Freediver needs
to understand partial pressures of
oxygen and acceptable exposure
times/doses, then applying an
appropriate maximum operating
High oxygen exposures can dull
our responses to the rise of carbon
dioxide. This means we don’t feel the
accumulation or rising PPCO2. This,
in turn, can cause us to experience
a much higher level of CO2, which
could affect us with a form of CO2
narcosis. Sometimes there can be
too much of a good thing.
I do have an adventurous side that has
me explore another side of freediving
that requires the right tool for the job
depth for the nitrox chosen.
Let’s look at a freediver for
example. At 95ft (29m) on 36%, a
freediver would be at a PPO2 of 1.4
ata (current accepted recreational
limit), allowing a single exposure
of 90min. More time than they
could even think of staying down
on a single breath! However if they
accidentally dipped down to 130ft
(40m), exposing themselves to 1.8ata
PPO2 they would have 2min at that
depth before CNS oxygen toxicity
was likely and CONVENTID might
rear its ugly head. That depth and
time is not uncommon for the trained
and experienced freediver. But 95ft
(29m) to 130ft (40m) is a pretty big
mistake not to catch, so let’s look at
it in another potential way.
Let’s say our hypothetical
freediver uses 100% oxygen
(normally reserved as the surface
recovery gas) and is playing in the
shallows on some extended breathholds. In 13ft (4m) of water, a PPO2
of 1.4ata would be observed with
a single 90min exposure. However,
if the freediver instead goes to 26ft
(8m) with a PPO2 of 1.8ata, the 2min
exposure and CONVENTID would
Handling oxygen becomes a
concern when dealing with mixtures
above 40%. This is really a concern
for the blender, not the consumer.
Staying with 32% nitrox is all you
require for the fun depth range down
to 130ft (40m). However, if you’re
the freediver using high mixes for
recovery, then handling is a concern,
as is having your regulators oxygen
serviced and maintained.
Cost is another consideration,
particularly if you buy your own
tanks and regulators plus the fills.
Along with that you have to prove
certification and many freedivers
aren’t scuba divers. This is one of
the reasons we are developing this
as a certification program.
Perfect recipe
Kirk Krack is
CEO and Founder
of Performance
Freediving
International, Rolex/
DAN Diver of the
Year 2016, and he
briefly appeared as an
underwater Batman
in this year’s Suicide
Squad movie
I’m a purist at heart. There’s nothing
I enjoy more than simply throwing
on my wetsuit, low volume mask,
freedive computer and long-blade
fins and going to enjoy an amazing
reef or get some dinner for the
evening while sharing the experience
with my friends. However, I do have
an adventurous side that has me
exploring another side of freediving,
which requires the right tool for the
job. Technical Freediving can be that
tool, when used with proper training
and a smart mindset.
This January I look forward to
exploring the wrecks of Chuuk
(Truk Lagoon) with six other scooter
technical freediving individuals while
my seven rebreather compatriots
look on. Wrecks, scooters, nitrox,
oxygen and a pair of lungs. The
perfect recipe for some adventure in
breath-holding.
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