Mythbusters had an episode that illustrated this very nicely, and Carrie kindly pointed out the relevant video on YouTube.
They stuffed a dead pig in a hardhat diving suit, dropped it to 100 meters depth, then drained the air pressure from the suit, subjecting Mr. Porker to 10 whole atmospheres of pressure.
The entire pig was shoved up into the diving helmet, and then the helmet caved in. Much blood ensued.
I should issue a gore warning here. Otherwise, enjoy!