When I use the tab key, sometimes it bounces me back to the surface of the water, other times it doesn't. I haven't figured out yet why it works sometimes and not others, but I suspect it may have something to do with the angle of the camera and whether there are rocks in the vicinity - it does seem to me that I've had better luck catching those underground views when I'm not near any large rocks, but I need more experience to be sure of that.