Fear of the water: more people than ever are getting sick, and even dying, from recreational water illnesses. Here's why it's happening, and what operators can do to keep their pools safe.

The kiddie pool at Six Flags White Water in Atlanta seemed like a safe enough place for 2-year-old McCall Akin and her mother to cool off on a hot day. Frequented by many toddlers such as herself, its shallow blue basin was carefully watched by lifeguards. But no lifeguard could save McCall from what was about to happen to her that summer of 1998.

A few days later, she started having severe nausea and stomach cramping. Her parents rushed her to the hospital, where she suffered from a stroke and several seizures before slipping into a coma. A few weeks later, she died.

The culprit? A bacteria known as E. coli that health officials later learned McCall ...