This sign at a public fountain in Louisville was designed to scare away the not-too-bright, which happens to be the exact kind of person who jumps in a public fountain. And if you're saying to yourself, "I don't get it," we've got some news for you: There are also high levels of hydrogen in public swimming pools. And sinks. Even the bottled water you're drinking right now. The world is a terrifying place when you didn't pay attention in science class.