There are some underwater concerts down here in the FL Keys, mostly gimmics I assume. I've never been and I'm not sure if there is actual underwater musicianship, possibly the playing of keyboards and midi percussion I suppose, but there are underwater PA speakers for the snorklers, scuba-dudes and free-dive swimmers. I doubt any of these events have ever been taped by a hydrophone wielding concert taper, but it's a brave new world of opportunity- no problems with patrons talking over the music or fear of frozen toes.