I think you are referring to the Eisbachwelle, Munich’s standing wave which was not created by the surfers, just exploited by them (and only the most famous of the city’s standing waves). It used to be forbidden to surf on it when it was still under state control, due to the danger (and yes, there have been deaths). The city swapped some land with the state to take control.
Yes, I live in Munich, and my office is near where this guy seems to have swum. But I prefer the subway, as it’s by far the fastest way for me. But yeah, Munich’s Isar river is also one giant party in the summer, so much so that now the Hellabrunn zoo is complaining about the smoke from all the barbecues.
