Photon Freedom is a great choice and if I were going any bigger I would go with a Petzl E-Light.
By the way many low energy lights (voltage?) don't need to be waterproof. I have seen several Photon models stay on while in a glass of water.
I saw a lot of these at SHOT show;
http://www.streamlight.com/product/product.aspx?pid=141
they are very small.
Bill