I remember doing those tests for Binnenschiffahrtslizenz in the late '70's. Not much fun, but at least very educational.
I spent most of my youth on the lakes around Munich.
I am not sure how the rules have changed, but most lakes there require a permission to boat. On the Starnberger See for example, there is a waiting list that right now is about 6 years long. Once you get your permit, you will keep it for 4 years, and then move over for somebody else. The permit holder has to be on board, and the Polizei spends their time checking ID's on the lake. My family has held an uninterrupted permit for approx. 25 years, by simply applying under another family members name as soon as a new permit was given.
Even German laws have loopholes!
I think sailboats without engines are exempt on some lakes but not sure.
It certainly isn't as easy as here to back up a trailer and drop the boat in...