I am not local but I'm not sure if the banks of the river near the park are conductive to a "falling in accident"? And even if that's a logical possibility, would that remove the notion of "suicide"?
I'm from the Appalachian Region, but not TN. I have been to Knoxville. We have folks who misjudge these mountains, and bodies of water, all the time and end up dying. Especially folks from out of state. If he wanted folks to think he went in at AFP, his body would have been found down river from AFP, not upriver, and in a cove.
The bridge at Georges Creek appears to be about 20' at it's highest point, and there is a spillway under it, that allows Georges Creek (which is actually a stream) to flow out and into that pool, then, underneath the bridge, and on to the other side, and on out into the Tenn. River. At the time of B's death, the water was fairly low, I think, in that area. Lot's of exposed bank. However, even if he slid down a bank and fell in, if intoxicated, combined with the shock of the very cold water, at night, it's very possible he'd drown, even in 5-6' of water, off the shoreline.
One thing that struck me was no scent outside the car, and his body being found in a cove. If you look down, from the previous map, at marker "B Georges Creek", there is a ramp, to drive right to the water's edge. Below is a photo of that ramp. If foul play, what easier place to put a body in the water.