S.K.
Hi J.,
It is a good idea to check with the pool where you will be taking your baby for swim classes as to what they allow.
I used the disposable ones at AVAC until one of the attendants there politely told me that they were not acceptable as they tend to rip and that the solid matter can then get into the pool.
They insisted on the re-usable diapers with the elasticated legs (which hold in the poop, but not all the pee). They also sold them in their store for a nominal fee (quite reasonable).
One word of warning - when changing out of the re-usable kind, check diaper first and remove it over a toilet or in the shower. It's deceptive how much is in there! And you can't always tell from the outside if it's pool water or pee!
For my son, I used the re-usable or the disposable under his swim trunks. For my daughter - she just has the re-usable and a swim shirt.
Hope this helps,
S.