Yes, there is a bit of a swim diaper in this. Swim diapers are not to hold number one. They should only be designed to keep two from floating away. The problem with the diapers that should hold one is that they get all bulky. We put a more stringent swim diaper under this, and it's great for his swim lessons. The reason I took off a star is that I wish they were more flexible like the pair of Speedos swim trunks that he used to wear when he was smaller.