submersibles
@magicaltrout The hatch (and windows) on Alvin taper so they seat more tightly the deeper you go. My photo of the hatch from inside is blurry (I was pretty damned excited!!), but it looks like there are some fasteners on the inside. Bolts on the outside sound like a Very Bad Idea. The passenger sphere is designed to be detachable from the rest of the sub and positively buoyant so the only way it wouldn’t be able to get to the surface is if it was wedged underneath something.
A Washington Post article suggested flammability concerns, which is terrifying and speaks to your Apollo 1 parallel…