SkyBlueFlux
Well-Known Member
Traditional subs can be opened from the inside. They have them spinney handle thingys. Sorry for the technical terminology.
I’m no expert but on a sub you can just build a door that’s 6 inches thick and slap a valve on it so you don’t have to bolt/unbolt it every time - makes it logistically easier but nobody would ever actually open the door while under water.
Submersibles don’t have that structural luxury, doors just become vulnerabilities to high pressure.