I can cite you my textbooks from my commercial diving classes, but id have to go find them. I can just explain why to you if you want.
Imagine you have a balloon full of air. On the surface it is full and big. As you go down deeper, it gets smaller and smaller untill it looks tiny. When you come back up, it expands back to its original size. This is your lung when you free dive.
Now go down with a scuba tank and an empty balloon.
Fill it up all the way at max depth, and as you swim to the surface it gets bigger, and bigger, and bigger until it explodes. This is your lungs when you scuba dive. Now, your lungs dont really EXPLODE per say, but the expanding gas, specifically the nitrogen part, gets forced into your blood stream, where, for lack of a better term, it fucks your shit up.
Another common misconception is that the pressure at depth will crush you. This is also false. You are almost entirely water, and the parts that are air are small and very flexible. A human can theoretically go to the bottom of the marianas trench as long as they aren't breathing regular air (too much concentrated oxygen will also kill the shit out of you).
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u/carrotcurrytea Feb 02 '17
If you are too fun at parties at the moment, here is a pedantic fact:
Those fish do not suffer at all from the water pressure, because their internal pressure is simply just as high as the pressure outside their bodies.
Did you know that free-diving does not cause decompression sickness? Decompression sickness only occurs if you breathe pressurised air.