Slider

Chester,
That actually helps to rule out the cooters. It is very likely a red-eared slider or yellow-bellied slider.

It was in Chickamauga Creek, what more habitat info would narrow it down?

It is impossible to tell form the photo what this turtle is and there is no habitat information to assist in narrowing it down either.

Team Brinez 1, I think it is unlikely Actinemys marmorata due to the fact that this turtle is in Tennessee. I don't believe they occur on the East Coast of the US.

It's possible that this is a species of Slider, but without a closer view I think getting a solid ID on this turtle will not be possible (unfortunately).