That's 20 percent of Americans urinating where others swim.
Besides being disgusting, peeing in the pool may be seriously harmful to your health.
In a new study, re-searchers from China Agri-cultural University and Purdue University looked at what happened when uric acid, a byproduct of urine, and chlorine combined.
The group found dangerous chemical reactions were a result of this unholy union.
The combo kicks up cyanogen chloride, a gas that can harm the central nervous system, heart and lungs if inhaled. Uric acid is linked to 24 percent to 68 percent of this byproduct in pool water, the scientists said.
And you can chalk up 3 percent to 4 percent of the harmful byproduct trichloramine in pool water to uric acid.
Nitrogen trichloramine (NC13) is a poisonous gas that can cause acute lung injury.
The buildup of this gas can be so quick and so severe that researchers studying a national swimming competition found that NC13 levels doubled after one day of use.
The gas levels increased as much as fourfold over the entire four-day competition.
Both of these gases have been linked to chronic health issues among swimmers.
How can we stop these chemical reactions from occurring?
Jing Li, professor of applied chemistry at China Agricultural University, told QZ.com that increasing the amount of chlorine in pool water would help in part. Another, much better solution: Don't pee in the pool. It is, as the study points out, "a voluntary action for most swimmers."
Sadly, this isn't a first report on human waste in swimming pools.
According to a May article by the L.A. Times' Amina Khan: "More than half of the public pools tested in a new study contained bacterial evidence that someone may have pooped in the pool."
Let's just get it together and make it to the bathroom, people.
Here are some other swimming facts from the latest survey:
•11 percent of participants admit to swimming with a runny nose
•43 percent said they skipped taking a shower before swimming
•6 percent admitted to swimming with a cold
•But less than 1 percent admitted to swimming while ill with diarrhea.