Freediving

[meglet]

I know I should know this as I did my PADI course at the end of last year but....

Why don't you get the bends whilst freediving?

[mibn2cweus]

The "bends" is caused by the decompression of nitrogen which has been absorbed in body fat. Absorption of nitrogen increases with increased pressure experienced with depth and the amount of time that air (which contains nitrogen) is breathed while under increased pressure. Not breathing air and brief exposure to increased pressure limit the absorption of nitrogen.

[jake-the-peg]

Note that whales can get decompression sickness
http://news.bbc.co.uk/1/hi/sci/tech/4122119.st m

It's just that humans cannot really stay at depths long enough for sufficient Nitrogen to become absorbed in the slow tissues like cartilage for it to be a major risk.

The big danger with free diving is the last 10 meters on the way up - this is causes the biggest drop in the partial pressure of oxygen and the greatest risk of blacking out.