[ak_111]

Interesting idea, I actually can't think of anything they are able to communicate that would aid in their rescue. They could probably signal if they are close to the surface, they won't be able to provide much more information on their exact location I think.

[ip26]

Identifying themselves to disambiguate from other random noises?

[ak_111]

The banging noise is already treated as non-random but that doesn't make it easy to locate, and they are presumably unable to locate themselves so won't be able to transmit any location details even if you gave them a few words worth of bandwidth, the best they might convey is how deep they are currently are "We are only a few meters above the wreck". for example