I saw something else stating even if there was a crack, the pressure of the water shooting through would have been enough to slice through anyone in the path. Eek
(I've not vetted this for accuracy)
There are cutters that use water at high pressures to cut through concrete, so it seems plausible that a fissure in the hull of a submersible deep into the ocean would create a stream with enough pressure to cut through flesh and bone.