I got a cellulitis infection in my foot from bacteria I most likely got while at a swimming hole. It was brutal, my foot swelled, was incredibly painful, and I spent a couple of days on an antibiotic IV drip in the hospital. The young man in the bed next to me was in even worse shape from ingesting bad water. He had to basically learn how to talk again, and had to be assisted in doing simple tasks by his mother. He almost died.
I still go swimming at swimming holes.
It's a chance occurrence, and that's life. Can't live in fear.