[stickfigure]

That's what they did? Alvin is an outlier; other bathyscaphes used the (tried-and-true) bolt-in method.

Assuming they're out there near the surface bouncing around in 6' waves and whitecaps, what they need isn't a door they can open and drown themselves with. Seems like what they need is a more effective location broadcast.

We don't actually know that they don't have good ways of being found. If they do, it makes it all the more likely that the sub is on the bottom :-(