Buoyancy is
the business end of scuba diving and has historically involved a cast of
thousands all the way from Archimedes and Charles Darwin to my instructor. People
(Tim Ecott for example) have written about it. NASA built the Sonny Carter Training
Facility based on its concepts. All this technology was developed to emulate
what a fish can do subconsciously with their swim bladder, which in evolutionary
terms is uncannily closely related to, surprise surprise, mammalian lungs.
The Fin Pivot
Lying
stretched prone and face down on the pool bottom, arms folded in front of you is
not the most graceful position for a diver to find himself in but it is where buoyancy
control starts. You take a small breath inwards to determine if your upper body
rises off the bottom. If it doesn’t then you pump a tiny bit of air into the
BCD, then breath in again. Surprisingly you find that your upper body rises off
the bottom leaving the edge of your fins remain apparently anchored to the
bottom; hence the term fin pivot. Breathe out and your upper body falls back
down. After a bit of practise by just controlling your breathing you achieve a somewhat
soporific state of weightlessness.
The Hover
Mastering the
hover takes years but it starts right there in the pool. The principle is
straightforward. Kneeling on the bottom, you are already negatively buoyant. If
you breathe in and you start to rise slowly then you can probably become
neutrally buoyant and maintain it by simply controlling your breathing. If you
don’t rise off the bottom, then pump a little air into your BCD and breathe in
again. If you start to rise off the bottom then you’ve nearly got it right. If
not breathe out and repeat the process.
Once you start to rise off the bottom,
then you can control your buoyancy by lung capacity alone and will not need to
depend on the BCD. Breathe in – rise,
breathe out – fall. How much you breathe
in or out will determine by how much you rise and fall. True mastery of your breathing
will get you to a point where you neither rise nor fall. That’s the art that
takes years but it is mesmerizing to watch divers like my instructors who have.
For now, time to go
topside.
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