I haven't heard of anyone doing it.
You could set it to track you, swim out, surf, swim back and in and retake manual control - but if anything at all went wrong you'd be screwed, and there's a pretty solid chance that it could potentially 'lose' you, in which case you'd need to redo the entire process - which would take quite a bit of battery life.
You'd be better of buying it, teaching a friend how to fly it, and then leaving it in their hands while you surfed.