I'd assume they'd make a great inner tube to float though! If they could master their legs and feet as pontoons and get the end of that tail going like a prop...
Why don't you try it and tell us how it goes?...Kidding! DON'T- lol. I've been told that when endagered they can inflate their bodies up, so I'd presume they could float at the surface for a little while and flail about...so I guess that's kind of like swimming.