I got one of these swim diapers in August 2010 for my then 15 month old and we used it for the beach and swimming pool and ever since for swim lessons. I love how easy it is to put on and take off! I'm generally not a fan of velcro (prefer snaps), but it's held up well through chlorine and washing. I make sure the velcro is attached when washing so it doesn't stick to anything else. It has picked up some fluffs from washing with towels but that'll happen with any velcro! I chose the Large in green Fishies pattern and it's adorable. My son is now 21 months old and 29 lbs and it still fits him great.
Be aware that reusable swim diapers are not made to absorb pee but this also means they won't absorb half the pool and become saggy! Disposable swim diapers will immediately soak up pool water and have no room for pee either! I just keep my son in a regular diaper until right before we're ready to go into the water.