Humans are designed for terra firma.
So taking the plunge and going diving
exposes the body to some foreign (and
potentially frightening) sensations.
Here’s what happens when you sink
below the surface . . .
On the way down
10 m Under pressure
Water is much heavier than air, so for
every 10 m descent the pressure on your
body doubles. This increasing load on
the eardrums and sinuses can some-
times have scary side-effects, such as
The protective pop To prevent
burst eardrums you have to keep
the pressure in your ears and
sinuses the same as the water
The handy Valsalva
manoeuvre involves closing the
mouth, pinching the nose
and forcing air through
the nose to “pop” the
ears and equalise the
15 m Getting
Every 15 m you
descend hits you
like a Martini
on an empty
30 m Drunk diving
Once you drop below
30 m, nitrogen in the
blood becomes toxic
and leads to
a mental state
similar to alcohol
be surprised if you
laughing fits or
40 m Too heavy to
Divers shouldn’t venture
down further than 40 m. At
this dangerous depth the pressure
equals 90 metric tons!
50 m Lights out
Light from the surface simply can’t make
it to this watery underworld, where it’s
darker than the middle of the night!
On the way up
Swimming quickly to the
surface causes masses of
nitrogen bubbles to form in the
bloodstream – it’s like shaking
a fizzy cooldrink can before cracking
The leads to decompression
sickness: your skin itches, your head aches and you
feel nauseous and dizzy. These symptoms get worse by
the hour once you’re back on dry land.
Decompression sickness, also known as “the
bends”, can be life-threatening. If just one large
nitrogen bubble reaches the brain or heart, it can
cause a stroke or heart attack. These bubbles can
also damage tissue, nerves and organs.
Do it right
When ascending, breathe rhythmically and correctly as you
swim slowly to the surface. Also, whether you’re going up
or diving down, make sure you swallow often to prevent
pressure building up in the middle ear.
Don’t wait to exhale
Holding a deep breath before surfacing quickly
is a recipe for disaster. Because air expands
dramatically as you ascend it could even
cause your lungs to burst. Large
bubbles can also stream straight
to the heart and brain,
resulting in loss of
consciousness or death.
Divers with “the bends” have to
spend hours in a decompression
chamber. The air pressure in the chamber
is lowered slowly to allow nitrogen to gradually leave the
diver’s body until normal surface pressure is reached.
Take it slow
Divers should never surface
faster than the tiny bubbles
How fast is that?
Surfacing at about 9 m a minute
or slower allows nitrogen
bubbles to seep out of the
bloodstream slowly and
be exhaled safely.
in a group or
with a friend
be shared if
Did you know?
person can hold
his breath for
30 to 90
All you need to know about diving
10 Tips for diving survival