new loop wrist bands

If you have the loop with velcro (although Apple doesn't call it that) some have reported that the hook portion eventually fails after repeated exposures. I would keep an eye on it. The new Solo loop would be great for water. And no, not all bands are water resistant.

If you wear the classic sport band make sure the bolt is securely placed and you have an sufficient amount tucked in. People have reported knocking it off their wrist.

As far as I know, all of the Apple made wrist bands for the Apple Watches are water resistant, just like the most of the watches themselves.