The science behind it is really interesting. I had always assumed that you'd get more buoyant as you went down and the pressure got higher; the thing is, buoyancy isn't about pressure as such, it's about relative density. Water is almost completely incompressible; even miles down, its density only increases by a few percentage points. But the main thing keeping humans buoyant is the air in your lungs, and your lungs are compressed as the outside pressure rises, making the airspace smaller and denser, until your average density is greater than the water's and you sink.
Yeah, I looked it up for the same reason, that's why I said I found it so interesting :) thanks for mentioning it though, I'm sure people will be interested to learn why.
Thank you for the explanation. This is entirely counter-intuitive to me.
Learned something terrifying today, is more like it. No wonder those big wave surfers talk about being unable to tell which-way-is-up when they get washed up by a wave.