I have used both IPlay the Shortini Set and Impse Vimpse for my daughter who has allergies to traditional diapers. We strictly use cloth. Both are excellent brands. IPlay has the swim diaper enclosed as part of the swim wear while Impse Vimpse is just a diaper that you can pair with a top if you want, place under a swim suit, or wear alone.
Styles come in everything from just pull on to snaps, to hook and loop closures. I do not recommend hook and loop for any child who can undo the swim diaper unless you put it under a swim suit or trunks-unless you want a bare bottom.
I have purchased my swim diapers from http://myswimbaby.com/ their customer service is fantastic. When I ordered I had wanted a different design which was available according to the computer. The information was not accurate due to it not updating. They contacted me immediately letting me know the problem and offering me a choice of selecting a different design or waiting until they got a shipment in letting me know they had no idea when that would be. There are other companies such as jilliansdrawers that sell reusable swim diapers as well.
T.