We bought this for our 2 1/2 year old and it has worked well so far!

Pros:
Saves on cost of disposable swim diapers - especially since he often goes in our pool for just a few minutes each day
We haven't found the need for more than one, it dries out in between uses no problem

Cons:
The white fabric has gone somewhat yellow :-) Stain removing washing has helped, but in future we might consider a colored swim diaper instead