RE: Tennessee River - watch for these guys!
Ya know, this reminds me of when I was 12 or 13.* My dad, 2 neighbors and I built a raft out of plywood and truck inner tubes, slapped it together with a little tarp to escape the summer sun and added a tiller.* Both the neighbors just had daughters, and my little brother was only 7 or 8, so was too young... so it was just the 4 of us.
We dropped this thing in the Sacramento River someplace above Sacramento (my memory escapes me exactly where) and drifted all the way down to SF Bay.* As I recall, it took us nigh on a week, since we pulled in to shore every night to camp, though we slept on the raft.
It's probably my fondest memory as a boy.