These are my favorite paddling shoes by far. I am a OC-1 paddler, and I also tube on occasion with my non-paddling friends.
As a paddler, I spend a lot of time kneeling in my canoe-- a position that from experience, can leave you very sore, and also lead to your feet "falling asleep" from lack-of blood circulation on the river. (Kneeling "pinches off" blood vessels). However, wearing my Chaco z-2's this sensation of "pins and needles" is greatly lessened by comparison to when I wear other shoes. I think it has something to do with how open these shoes are, and how much fantastic arch support they provide.
As far as swimming with these shoes goes, I find it relatively easy. Unlike other sandals on the river, these shoes' tight straps hold the footbed close to your foot- thus minimizing the drag created by the current on the shoes.
Good shoes - good buy - good luck - and happy paddling!