This was a controlled depressurization (they used a release valve and let the pressure creep in). This shows what the pressure can do over time. Now image that be happening instant because the structure holding back the pressure failed all at once.

Mythbusters - Diving Suit Decompression (NSFW - gore)
Now imagine this, but deeper down, where the water pressure is even higher

Edit: Mythbusters - Tanker Implosion (SFW)

Another good video for perspective. The pressure the sub was going under was 519x GREATER than the pressure difference in this video