ummm, the actual Ruhr river is like 2 meters deep!?! and you couldn't turn anything bigger than a canoe (not a type II uboat, an actual canoe) around in it without a crane.
But it would be quite something to see, maybe surf that wave with your uboat.:hmm:
perhaps sailing up the mississipi a ways to attack oh, I don't know, the port of St. Louis would be more feasible