From what I understand, naval submarines typically have a signaling device called an EPIRB mounted in such a way that it's released automatically if the sub dives significantly below crush depth and/or if a switch isn't activated on some set interval. Then it pops up on the surface and says "Hi, wreck here."
I don't think the former system would have worked here anyway, since the sub is supposed to get very close to the bottom.
They had this but there were problems with it, if I recall correctly. So it would be disabled in "times of war" or whatever because if it accidentally popped off it was not a good time for you.
I don't think the former system would have worked here anyway, since the sub is supposed to get very close to the bottom.