A couple others-

I have friends who used to owned a raft rental busdiness on the Yakima River. My buddy and I had rented a raft from them to do some fishing. Another couple of guys showed up to rent a raft also, but just to float the river, not fish. We loaded up the rafts and headed upriver to the put in.
We get the rafts unloaded and get ready to launch. My buddy who owns the rafts gets ready to take off. One of the guys in the other raft then asks with a bewildered look on his face " Which way do I go?". My friend turns around and says "most folks go down river, but you can go upriver if you'd like". I couldn't stop laughing the whole day.

This one was conveyed to me by a buddy. He was fishing on the Yellowstone River. The put-in was at a bridge. One of the fellows he was fishing with was a fairly well know physician. After floating many miles on the river, they approached the take out, which was also at a bridge. At this point, the physicians says, "Hey, I recognize this place, this is where we started this morning". My buddy said the guide had to drop the anchor because he couldn't row due to laughing so hard. He always jokes now about having floated the worlds only round river.