do not swim when you have diarrhea. This is especially important for kids in diapers.

do not swallow the pool water.

practice good hygiene. Shower before swimming and wash your hands after using the toilet or changing diapers.

take your kids on bathroom breadks or check diapers often.

change diapers in a bathroom and not poolside.

wash your child (especially the rear end) throughly with soap & water before swimming.