Michele Hlavsa of the U.S. Centers for Disease Control and Prevention said the idea that swimming pool disinfectants kill germs instantly is a myth.
Hlavsa said that's why it's unhealthy to treat the pool like a toilet. People should shower off any germs before jumping into the pool, Hlavsa said.
People just want to have fun in a pool, but Hlavsa said carelessness in a swimming pool, wading pool or hot tub can lead to a variety of diseases.
"People could get gastrointestinal infections, viral meningitis, ear infections -- also known as swimmer's ear -- but the most common infection is diarrhea," Hlavsa said in a statement.
To prevent illness, Hlavsa advised to not swallow the pool water or swim with open sores.