Look what happens to the boat (actually two sailboats are tethered together). Notice how they go down in front of our eyes as the water is lowered before the locks are opened for them to proceed! And this is only one of the few locks! Crazy engineering feat.

To understand the engineering challenges, simply think of the four ropes that are tethering them to the land so that they do not hit the walls. How do you deal with the fact that the ropes now need to “give” as the boat gets lowered?