This is one of the best great bad ideas in a long while, Marty McFly: Waterskiing on a fountain. It looks like it can be a lot of fun, all the way to the hospital.

It's pretty simple: You just need a large fountain, a cable, a traffic sign and a car. Find a large fountain with a big water surface (lots of these space wasters in Europe), connect cable to car, and use a traffic sign post as a pivoting point to get more control. [Thanks Roberto!]