Sure, but it's not always obvious when a kid wearing a swim diaper poops. And they don't always tell you. Especially if they know it means they have to get out of the pool to change the diaper.
Swim diapers basically keep the _turds_ stationary. Water will still chew away at it and disperse poop everywhere, so its basically run out of the water when an "accident" happens. Still better than solid poop floating around I guess, but also, potentially, really nasty.
