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?
If the imploded it's over. If they are trapped on the bottom at that depth, I doubt there is a DSRV that can reach them.
Only another sub of the same diving capability has a chance and that could be days or weeks away.