There is another option to consider--something like the Hanimex Amphibian. Basically, a point-and-shoot in its own housing. It is sort of a precursor to the Sea and Sea cameras. They are cheap.
Here is one with a flash that didn't sell on eBay for $25
The off camera flash is a good idea to reduce backscatter (think Redeye for every speck of dirt in the water).
It would give you something to shoot with. If you lose it or it floods, who cares?
As I recall, these images were taken with the Hanimex--