Each summer, millions of Americans seek relief from the heat at the public pool ... despite the fact that the Centers for Disease Control release a report each year warning about all the bacteria that also goes for a swim in these pools.

A brand-new report from the CDC found that more than half the water samples they took from public pools contain E. Coli bacteria from fecal matter. It turns out that swimmers see water and assume it's just a big toilet.

The CDC says there are two ways the fecal matter makes it into the pool. First, it comes from swimmers who have, what the CDC calls, a "fecal incident." Second, it comes from people who don't shower before entering the pool, something that 70 percent of people say they don't do. So have fun this summer, but maybe keep your head out of the water. (CDC.gov)