This is a basic explanation of free diving. If you have a better
WU, then please post it and I'll be happy to step aside.
Summary
Free diving is quite simply diving underwater while holding ones
breath.
Free diving is different to SCUBA diving because SCUBA divers use an air
tank. Almost everyone who has been swimming has "free dived" by simply
diving to the bottom of the pool, or the beach, etc.
Many would think that free diving is an inferior form of diving
compared to SCUBA diving, after all, what can a free diver do that
a SCUBA diver can't? Actually, quiet a lot, a free diver can dive unencumbered,
any time, time after time, and experience being underwater in a more natural
manner. As a SCUBA diver myself, I can't say I particularly enjoy the
experience, but many find it great.
Technique
Everyone who has held their breath knows that after a short period
of time, your lungs begin to feel like they are on fire. This is
not caused by the lack of oxygen, but the build up of carbon dioxide.
Generally when you experience this sensation you still have plenty of
oxygen in your lungs, which is were hyperventilating comes in.
By hyperventilating you purge your lungs of most of the carbon dioxide that
is always in them. Thus allowing you to fill your lungs with more oxygen
and preventing the breath reflex from coming in too soon.
Warning: Over hyperventilating can have the opposite
effect and can even cause you to loose consciousness and can lead to
drowning and death.
Competition free diving
There are two main categories of competition free diving;
variable ballast and
constant
ballast.
Constant ballast
In this category there are 3 subcategories. Unassisted, line assisted, and
equipment assisted.
Unassisted refers to the free diver diving while under his/her own
power without using an guide lines or propulsion devices.
Line assisted refers to the free diver diving using a static vertical
line to pull him/herself down to the target depth and up to the surface. No
other propulsion device is allowed.
Equipment assisted refers to the free diver using self powered
propulsion device (eg fins).
Variable ballast
This category is broken up into 2 subcategories: Limited and Unlimited.
Limited refers to the diver using one a guided ballast device for the
decent. The diver may use a propulsion device (eg fins).
Unlimited refers to the diver using a guided ballast device for the
decent and a guided flotation device for the accent.
Dangers
I won't even begin to go into the numerous dangers there are with
free-diving. If you attempt to override your bodies natural defences
against suffocating by hyperventilating or using other special techniques,
you run into dangers. Much like with SCUBA diving, you should consult
a trained professional before attempting free diving.
Records
These change over time, and by the time you read this, these are
probably wrong.
No limits: 1999: 150m (492ft) Umberto Pelizzari
Variable weight: 1998: 121m (397ft) Gianluca Genoni
Constant weight: 1999: 80m (262ft) Umberto Pelizzari
References:
Limited personal experience
http://www.divingfree.com/
http://library.thinkquest.org/28170/45.html
http://www.freediving.net/historia.htm
http://www.geocities.com/~freediver/freedivingpage.htm