When a spacecraft performs a splashdown maneuver, a recovery team is standing by to retrieve the capsule and its human contents quickly. A flotation collar is deployed to increase buoyancy and prevent the spacecraft from sinking. If, however, the spacecraft did sink, would it be able to withstand the pressure of the deep?
Structurally speaking, what are the differences between a spaceship (full of astronauts) floating in the vacuum of space and a submarine (full of seamen) floating underwater in an ocean?
(This question stems from having recently watched the rather gratuitous opening sequence of Star Trek Into Darkness where the Enterprise is hidden underwater in an alien ocean.)