More than half of the public pools tested in a new study had bacterial evidence that someone may have pooped in the pool.
Federal investigators worked with local officials last summer to collect samples from pool filters at 161 pools in metro Atlanta.
Among the 161 samples, 93 - 58 percent - had Escherichia coli, a bacterium that lives in the digestive tract of humans and warm-blooded animals.
Swimmers likely delivered some of it into the water by failing to take a thorough, soapy shower before entering the pool.
Pools in private clubs were less likely to have E. coli in their filters, but investigators still found it in 49 percent of cases. Municipal pools had the highest incidence of E. coli, 70 percent, followed by water parks, at 66 percent.