In 1998, I lived just south of Munich for a couple of months leading into winter. It's a really, really gorgeous area and I loved my time there, but I never saw this on any of my trips into the city.
River Surfing in Munich Germany from James Kamo on Vimeo.
River Surfing in Munich's English Garden from Snehal Patel on Vimeo.
You can read a good article about it here.
P.S. Form a queue!