Surf's up in 1929 Munich as shown in this British Pathé newsreel of the city's new indoor wave pool. A series of paddles behind a net is used to push out the waves. The swimmers are admonished to not swim under the net. As for the “Indoor Surfers” of the title, it apparently alludes to visiting Hawaiian surfers and their redwood boards, but they are no where to be seen in the clip.
We learn: "This is the new kind of swimming bath that is becoming the rage of Germany." And, "No more placid waters for bathers -- the mechanism behind the netting keeps everything moving."
It is fun to contemplate that perhaps the Hawaiian surfers included Duke Kahanamoku and his brother Samual who visited Munich about this time. They frequented Europe for the Olympics, and even as late as 1932, Duke was an alternate on the U.S. Water polo team. One look at the surfboards of the day gives a hint why they would not be used in this pool.
What is interesting to note that these early efforts to generate artificial waves are found in what is now present-day Germany in Bavaria and around Munich.