C is taking swim lessons this fall. The description says anyone in diapers must wear "tight fitting rubber or vinyl pants over swim diaper". What is this? They sell them at the shop at the pool but if I can prepare ahead of time I'd rather. I've seen similar wording at a lot of swim lesson places but no real clarification on what that is. Reusable swim diaper over disposable?

Believe me, I do not want to be responsible for a code brown!!