Does my child have to be toilet trained to use the pools?
Traveling with Infants & Young Children – Frequently Asked Questions
Yes. The U.S. Public Health Service requires that only children who are toilet trained are permitted to enter swimming pools and spas aboard cruise ships.
Even if your child isn’t toilet trained, he or she is welcome to enjoy the water play areas on board each ship while wearing a swim diaper. These areas include Nemo’s Reef on the Disney Dream and Disney Fantasy, Nephews’ Splash Zone aboard the Disney Magic and Dory's Reef aboard the Disney Wonder.