text: There is a factor called "Crush Depth".  Crush depth is the depth at which the submarine's structure could collapse due to extensive water pressure of the surrounding.  WWII U-Boats reportedly had a crush depth of 200-250 meters.  Modern nuclear propulsion submarines (although not tested) could have crush depths of just above 700 meters.\n\nTo get the "feel" of it I suggest you watch the movies "U-571" starring Matthew McConnaughey, and "Crimson Tides" starring Gene Hackman and Denzel Washington