Well, I would feel it falling off so I would dive and get it back. I'm a surfer so I can hold my breath for a long time. I wouldn't leave the water until I get it back. If I can't I'd shout out to whoever was there with me and ask them to bring my clothes.
...my 코멘트 would be kinda inappropriate I think, so I'm going with this answer.. But um, somewhere in my mind it'll think everyone is happy now because their wish has been fulfilled. Just walk around naked xD