One of the articles mentioned that the means of communication from the sub to the ship was a SSBL(super short base line) acoustic transponder. SSBL is also a method of determining position, which I'm sure the ship uses to monitor the sub. We use them to track the position of our ROVs on my ship. These mini transponder beacons are always housed on the outside of the ROV, I don't see why it would be any different in this situation. If you don't regularly replace the zincs and the seals in these transponders, water will find its way to the battery and electronics and destroy it quickly. My thoughts are that if the submersible was crushed, the beacon would still be active. Failure of these transponders can be pretty common if they aren't maintained. For something carrying multiple people on board, I'd have multiple transponders on the craft.