I tubed down this river a few days ago. I got a couple shots before my camera failed from drained batteries. Next time, I'll be better prepared.
I keep my equipment in a drybag. Once I was comfortable with how the water was flowing, I pulled my camera out while still tubing. I was careful though :)
Here is one of my better pictures. I believe its a Texas River Cooter, a subspecies of the River Cooter. There seems to be some debate if its a subspecies or its own species.
Links
San Marcos River: http://en.wikipedia.org/wiki/San_Marcos_River
Texas River Cooter: http://en.wikipedia.org/wiki/Pseudemys_texana
Also, if you decide to do water photography, but the best no-questions-asked warranty you can afford for your camera and lenses.
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