Surfing in the middle of a landlocked city

The sign reads "Surf-ing and bathing forbidden," but as you can see, it's not strictly enforced. We visited Englischen Garten (a huge park in Munich) yesterday, where a fast-moving river creates constant waves in a small area under the bridge. It's nothing compared to the ocean (the surfers have to go one at a time because there's not much room), but I guess you can't be too picky when you live in southern Germany.