My warm-weather standbys are plain old Chacos, w/o the toe strap.
For the sort of funfest where you have to get out a lot and horse your boat over rocks, I wear the NRS Scout watershoes.
They're reasonably comfortable, well-made, and I can walk several miles in them barefoot without blisters. (Right now on sale for $38.95 which is a good deal). The NRS river shoes dry out pretty fast and if you pack some good wicking socks, synthetic or wool blend, you can do an emergency walkout without severe harm to your tootsies.
(The old gray-soled Chacos are unbeatable for friction scrambling on slickrock.)
For cold water, I add neoprene Gator Sox, the basic type and the pair I bought for paddling Sitka Sound with fleecy linings. Both are thin enough to wear with the Chacos and NRS river shoes.