Horse-surfing...
...looks like fun. They do it in Baule, on the west coast of France. Not to be confused with horse-boarding, which is on skateboards. It has become so popular that a training centre has opened and Britain’s first championships are to be held this year. Personally I'd go for the option over the water. You don't need as much body armour, and you're less likely to end up wrapped around a tree with some barbed wire in your thigh.