As anyone who's spent any time at one of our beautiful public pools (ahem, McCarren Park Pool) already knows, you take on a lot of risks in pursuit of a chlorinated respite from a sunny summer day. There are long lines, limited space, fist fights, unsanitary conditions, and um, the occasional "brown cloud." Except, according to the CDC, those brown clouds aren't as occasional as we'd all like to believe.

A new CDC report found genetic material from E. coli bacteria in 58% of public pools they tested last summer. This means that "swimmers frequently introduced fecal material into pools." How did it get there? They found that most came from incidents of defecation in pools, but also from swimmers not showering properly before getting into the water. It turns out the average person has 0.14 grams of fecal material on their "perianal surface" that can rinse into a pool if a person doesn't shower first—so you can only imagine how much a not-so-average person might have on them.

"Chlorine and other disinfectants don't kill germs instantly," said Michele Hlavsa, chief of CDC's Healthy Swimming Program. For that reason, they stress that swimmers need to shower BEFORE getting into the pool, not swallow the water, and ya know, perhaps stay as far away possible from pools if they've eaten Mexican in the last 24 hours. When in doubt, listen to The Beach Boys' advice: