When researching the history of whitewater kayaking online, I've encountered a few articles on Wikipedia and blogs that say that Hitler effectively banned the sport in 1933, and the ban remained until the allies lifted it gradually from 1946 through 1948.
Here's the Wikipedia article
I haven't been able to find more info on this through mere googling. It's an interesting bit of trivia and most of the whitewater people that I mention it to have never heard it before. I'd really like to know the whole story, so maybe someone here is aware of the story or could point me to a helpful book.
This is an interesting question as I have never heard of this before. The Wikipedia article doesn't cite any sources but mentions that the Allies lifted the ban on river travel. This could mean that the ban wasn't restricted to Kayaking but all forms of water sports. However, those sports, especially Kayaking, were huge among the Hitler Youth and even the Bund deutscher Mädel, the Nazi Girl's Organisation. The Vorschriftenhandbuch der Hitler-Jugend, sort of the manual of the Hitler Youth from 1942, expressively mentions Kayaking as a form of sport girls could do.
The only explanation I could think of, and always keep in mind I'm not certain such a ban ever existed, is that Kayaking outside of the Hitler Youth could have been seen as illegal Bündische Betätigung, that is: being part of a youth organisation not affiliated to the Nazi Party, which could lead to grave punishments.
This is an interesting topic and I'd love for other people to chime in, as I have never heard of it before. I'll check on it later and go to the library to see if there's something to find out there.