5 ways to swim safely this summer

THAT GLISTENING SWIMMING hole might look-and feelrefreshing on a sweltering day.

- ANGELA HAUPT

But writhing in pain from stomach cramps, nausea, and vomiting? Staring at the bathroom ceiling instead of the blue, sunny sky? Not so much.

Jumping into even the prettiest and clearest rivers, lakes, creeks, and other natural bodies of water can expose you to a cesspool of unpleasant and invisible fellow swimmers—most commonly bacteria, viruses, and parasites. “These germs are microscopic, so you're not going to be able to tell they’re there,” says Bill Sullivan, a professor of microbiology and immunology at the Indiana University School of Medicine and author of Pleased to Meet Me: Genes, Germs, and the Curious Forces That Make Us Who We Are. “Swimming is a great, fun activity—don’t get me wrong. But you do need to be mindful that there are dangers that lurk out there.”