Memorial Day is almost here, bringing with it a summer of bad 3-D movies, sunburn, mosquitoes, vacation rentals that smell oddly of grandma, people in shorts, and of course, trips to the local swimming poo.

No, that wasn’t a typo. Today, the Centers for Disease Control released a report on the tiny critters floating in pool water. According to the CDC, 58% of the pool water samples tested positive for E. coli, the classic marker for fecal contamination.

Though this does confirm our worst suspicions, we honestly expected the number to be higher.

“Finding a high percentage of E. coli-positive filters indicates swimmers frequently contaminate pool water when they have a fecal incident in the water or when feces rinse off of their bodies because they do not shower thoroughly before getting into the water,” writes the CDC, which does add that none of the samples tested positive for E. coli O157:H7, a strain of the bacteria that produces toxins and can cause illness.

So folks are pooping in the pool, but the E. coli won’t necessary get you sick.

What could get you sick is the Pseudomonas aeruginosa, found in 59% of samples. This stuff can cause skin rashes and ear infections, but is likely just a result of natural environmental contamination or contamination introduced by swimmers.

On the up side, Cryptosporidium and Giardia, two nasty buggers that are spread through fecal matter and which can cause diarrhea, were only found in less than 2% of samples.

It’s worth noting that the study only looked at public pools, but not water parks or residential pools.

“However, it is unlikely that swimmer-introduced contamination, or swimmer hygiene practices, differ between pools in the study and those in the rest of the country,” adds the CDC, which recommends the following to lower the odds that people are swimming in E. coli and other icky stuff:

Do not swim when you have diarrhea.

Shower with soap before you start swimming.

Take a rinse shower before you get back into the water.

Take bathroom breaks every 60 minutes.

Wash your hands with soap after using the toilet or changing diapers.

Check the chlorine level and pH before getting into the water. (Proper chlorine (1–3 mg/L or parts per million [ppm]) and pH (7.2–7.8) levels maximize germ-killing power). Most superstores, hardware stores, and pool-supply stores sell pool test strips.

Do not swallow the water you swim in.

Parents of young children should take children on bathroom breaks every 60 minutes or check diapers every 30–60 minutes, and diapers should not be changed poolside, where germs can rinse into the water.

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