Locks over the Rhine

Another memorable experience was the visit to the French border.
The Rhine acts as a natural boundary between Alsatian France and German Baden Wurttemberg in these parts.
The trip to the border was uneventful except that I noticed that the autobahn (high speed motorway) had a lot of motorbike riders on that sunny day. It was quite hot for that summer, but they were all in the same stereotype boots, jacket and goggles pulled over their eyes.
Also I noticed that some of the cars had bicycles or small boats hauled on top of them. Families out on a boating trip perhaps, or simply cycling in the countryside enjoying an unusually hot summer, I guessed.
The first question that came to my mind was why the Rhine needed water locks. (The ones like those over the Panama/Suez canal). The answer is that at some sections the water is too rapid. I guess, too fast for a moderate sized boat or a tug to safely navigate.
The upriver boats enter the first lock whose floodgates are then closed and water fills in calculatedly through sluices. Once the water level nears the level of the upper body of the river, the lock is opened, water fills in, and the boat(s) continue on their journey.
And it is vice versa on the other lock.
There were a good many people on joy cruises in addition to the commercial tugboats.
Some pretty beauties on fancy boats were actually doing crew work.
Wow! Those beauties really knew their ropes.