10 out of 10 points for innovation. 1 out of 10 points for something that makes sense. I’m giving them 1 point for having the idea of signaling when a diver (may be) in trouble. And I do like the idea of a device for returning the body to the surface; kind of like the solution of putting a stake in the coffin lid to make sure that everyone who is buried is actually dead. Sorry, that was macabre.
What about a device that alerts Diver 2 when Diver 1’s breathing seems to be in trouble? Of course, the audio portion is useless to anyone else in the water, since we generally can’t tell direction based on sound u/w (although if we’re always aware of where our buddy is maybe that wouldn’t be necessary).