In one of the parks in Munich, there's a (concerningly!) fast river. It occasionally made a natural standing wave but in the 1980s, by the insertion of a railway sleeper, the local surfing population discovered the could make it more permanent. It has marginally more control now, but the principle is still the same.
All the surfers were amazingly skilled, but this guy seemed to be able to hold his own for just a little longer than the rest. Absolutely amazing to watch, all of them.
