I have two of those (from Lowes) on my front porch. I find them comfortable. They flex a bit, which makes them more comfortable than a heavier duty version. They don't hold up all that well in the sun (a couple seasons, maybe), but they're cheap enough to buy 10 of 'em and still be ahead when compared to a "real" Adirondack chair...
They're light, and they stack. Never had one in the pool so I can't say if they float or not. For 20 bucks you can't really go wrong giving one a try...