Beachgoers who play in the sand are at risk for gastrointestinal distress.

The ocean is beautiful, but you know that open water has risks, such as violent undertows that can trap swimmers under crushing waves. (That’s why it’s important to pay attention to posted signs and stay within areas demarcated by a lifeguard.) But here’s some bad news for sunbathers: You’re not totally safe on the sand, either.

Contaminated sand

It’s fairly easy to play hopscotch around broken glass and grease-stained garbage. It’s a lot trickier to try and sidestep tiny particles of fecal matter sprinkled all over the shoreline.

A new study in the journal Environmental Science & Technology found that many beaches are teeming with strains of bacteria that are more resilient on land than they are in the water. The researchers from the University of Hawaii at Manoa reported that some microbial colonies decay slower in the sand than in seawater.

And when those bodies of water are contaminated with noxious runoff—a disgusting trend associated with increased precipitation and sewer overflows—that can translate into some gnarly pathogens lounging near your beach blanket.

The researchers found that many types of “fecal indicator bacteria,” especially C. perfringens—a common source of food- and waterborne illness—linger in the sand. These pathogens are implicated in “recreational water illnesses,” which increased by 200 percent in just four years, according to the Centers for Disease Control and Prevention.

And no, you don’t have to eat the sand in order to be at risk. A previous study in Epidemiology found that people who had dug or been buried in sand reported a higher rate of subsequent gastrointestinal distress and diarrhea than revelers who didn’t have skin-to-sand contact. The Environmental Protection Agency recommends avoiding beaches following a heavy rainfall, and forgoing sand frolicking if you have any open cuts or scrapes. (Maybe you want to reconsider constructing epic sandcastles.) And if you do wade into the water, try not to gulp any—that puts you at increased risk of gastroenteritis.

Here are two other ways of getting sick near the sand:

Enormous algae blooms

As CityLab’s Mark Byrnes wrote, massive, slimy blooms—such as the one in China’s Yellow Sea that clocks in at one million tons—can be fun, at first: You can play dress up with the green stuff and turn yourself into a sea monster. But things take a turn for the gross when the algae starts decomposing, releasing smelly, toxic hydrogen sulfide gas.

Algae blooms can also contribute to illness, though largely through eating fish that have been swimming in the stagnant water. For instance, ciguatera—contracted via consuming barracuda, grouper, or king mackerel containing the microalgae Gambierdiscus toxicus—can result in vomiting and neurological symptoms.

Venomous beasts

Fearsome creatures, like the terrifyingly ugly blobfish, aren’t confined to the deep. So far this summer, the New Jersey shore has been littered with gelatinous jelly fish and man o’ wars, which use their tentacles to paralyze victims. The stings are rarely fatal, but can lead to scarring, muscle spasms, and weakness. They can still sting when washed ashore, so beachgoers should leave a wide berth, Paul Bologna, director of Marine Biology and Coastal Sciences Program at Montclair State University explained to the Asbury Park Press.

Top image: Prudkov/

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