Btw: this isn't a phenomenon exclusive for Germany, there are many other navigable aqueducts where there is a need of crossing a natural river with a canal.
I think the craziest navigable aqueduct isn't in Germany but in the UK: it is the Barton Swing Aqueduct. It's a trough filled with water which can be swung 90? so bigger ships can pass the river underneath. I think that's even more crazy than a ship lift which just goes up and down (well, the Falkirk wheel which is also located in the UK is a crazy ship lift, but at least it is balanced out so for the rotation only needs a 20 kW-engine...).
That's when I try to involve someone else in the conversation so that there is a chance that a name might be uttered and my ass saved from... asking a question that doesn't really matter or offend anyone in the first place.
first time i see it for bicycles, but i've seen that done for cars when there is a right turn. to not hold up traffic, they have to take the left exit, and wait till no car is coming before crossing...