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!
They have very high arch support so with that tidbit I'll also warn that if you go from something like the Hurricane or Newport give yourself some time to adjust, don't just throw these on and go for a 3 mile hike, your feet will hate you. I learned this the hard way too. That being said, if I'm not going to work, odds are in wearing these around. I even have z strap tan lines on my feet.