The U.S. Centers for Disease Control and Prevention (CDC) issued a warning this month about a fecal parasite that can be found in swimming pools, and it causes terrible symptoms like stomach cramps, fever, vomiting and “the runs.” In medical circles, this nasty bugger is known as cryptosporidium and it can reportedly survive for days in pool water. Crypto can enter the body when a swimmer swallows contaminated water, and contamination comes from, you guessed it, poop. An alarming survey from the Water Quality & Health Council found that “half of Americans use swimming pools as communal bathtubs,” which translates to 24 percent saying they’d jump in the pool within an hour of having diarrhea and 48 percent admitting they don’t shower before swimming. How to protect yourself? Do your part—don’t swim in a pool for at least two weeks after suffering from a stomach ailment, and keep your mouth closed while swimming!