Looking to stay cool this summer? You might want to stay out of the water. According to a new survey by the Water Quality and Health Council, one in five Americans admits to urinating in public pools — and that's just the beginning of the "nasty germs" lurking below the surface. Here's what you need to know before diving in:

What germs are in there?
Seven out of 10 swimmers reportedly don't rinse off or shower before jumping in the pool, making for a potent stew of other people's sweat, cosmetics, feces, and other dirty stuff. Harmful germs ranging from Giardia, E. coli, and cryptosporidium parasites have all been shown to spread in public pools. All three are known to cause everything from diarrhea to dehydration to vomiting.

But doesn't chlorine kill all the bad stuff?
Only to a point. (Too much chlorine is bad for you, anyway.) And contrary to popular belief, it isn't chlorine itself that irritates eyes: It's when chlorine comes into contact with high levels of contaminants that swimmers experience eye redness and the water begins emitting a "strong chemical smell," says Michele Hlvasa, chief of the CDC's Healthy Swimming Program. An ideal swimming pool should be odorless, as chlorine only really smells when it's interacting with contaminants. If the chlorine is pungent, you might want to cool off elsewhere.

So... what should I do before wading in?
"It may seem counterintuitive, but it's important to shower before you jump in the pool to help keep swimming healthy for everyone," Dr. Chris Wiant, chair of the Water Quality and Health Council, tells CNN. Indeed, "not showering before swimming is equivalent to recycling bath water," says Paul Friswold at Daily RFT. That neighbor "who just mowed his lawn, then walked directly to the pool and cannonballed into the deep end? He's a main ingredient in the filthy human gumbo that is a public pool."

How can I tell how dirty a pool is?
Swimmers wary of a public pool's safety can request free test strips to check pH and chlorine levels before diving in. 

Sources: CDC.govCNN, Daily RFT, LiveScience