[pfflier]

If they are on the bottom there is zero chance for rescue. It would take too long to even get another capable sub to them.

Once they get there, the only method of recovery would be to attach flotation devices. Not a chance they could transfer passengers.

[desertsolitaire]

I’m not even certain that a commercial sight-seeing submersible HAS a universal escape hatch built on it to hook up for rescuing passengers. Are they required to be present on every submersible?