I doubt very much that the pings you hear are from submarines, one of the primary objectives is to stay covert, dashing around pinging their sonars willy nilly kinda defeats that. Saying that though, it may be sonars from a small boat or fishermen, fish finders. I doubt very much they’re listening for you, but some Black Sabbath tunes may provide some clear water around you if they wereWelcome aboard! Or, in your case, should I say, welcome to the MOB lot?!
Hey, not to prize anything out of you, but on occasion, driving my DPV in the waters off our fair island, I would hear certain regular pings… (can be rather annoying, I have to say). If I brought an mp3 player in a waterproof canister on a dive, what would be the sort of music to play, you know, to mark my territory? Would my man Ozzy still be appreciated?