Surprise, surprise. Swimming is good, clean summer fun for small children—but University of Florida experts caution that swim diapers won’t necessarily keep the water clean, and that could spell trouble if sick kids go in the pool. A common illness called Norovirus infection can cause vomiting, abdominal cramps and diarrhea. And for children suffering from such an infection that last symptom can render swim diapers ineffective, said Fred Southwick, a professor and chief of the infectious disease division at UF’s College of Medicine. U.S. Centers for Disease Control and Prevention officials say no swim diapers are leakproof and that no manufacturer claims its products prevent diarrhea leakage. CDC devoted a page to the topic: . Children with diarrhea shouldn’t be allowed in pools, regardless of their swimwear, Southwick said.