I've worked on some whitewater rivers and they definitely can destroy just about anything. If the river is rough I would either portage the big rapids or use a standard raft. As far as flat water goes a canoe would be about the cheapest/free (i've seen a lot of canoes just rotting and going to waste in peoples yards) thing, and it is fast and efficient. Plus you can sleep in the bottom of one if it doesn't have too much stuff in it. I've never build a raft though.