Have you looked into a GoPro? Seems like it would get you the best bang for you buck photo wise.

If that's a bit too expensive a cheap waterproof phone case meant for taking underwater photos can work wonders. The shots will be a bit cloudy and unfocused compared to a GoPro but they'll still be really good and it's a $20 or so investment. I got one in Key West prior to a expedition. It worked wonders and my phone never got a drop of water in it.