I was just up there a few weeks ago for three days of fishing. As I always do when fishing up there, I fished long stretches on foot each day, and on at least two of the days that I recall, I saw guys floating the river in float tubes. Maybe it's me, but over the last ten years or so of visiting up there, I've seen a progressively wider variety of watercraft on that river. Where it seems like it used to be almost exclusively the traditional Au Sable river boats and occasional canoes, I started seeing pontoons some years back with more frequency than ever before. Now more recently I've seen float tubes too. Especially on the mainstream, it's such a slow flow and shallow water in most cases, I can see where that would be a practical means to get around. I think I'd still want a pontoon or something with oars to be better able to make a radical course adjustment if I was coming up on a sweeper or something, but I guess if you were keeping your eyes far enough downstream, you could navigate effectively even with a tube. Either way, I'd only use it for navigation between points that I'd fish while wading, but that's just me...