The Horse and the stream joke.

I found this joke in an old jokebook.

A man is on his way to buy a horse from the local market. Whilst on his journey, he has to walk over a large hill. When he gets to the marketplace, there is a fine looking mare that's on sale for dirt cheap. The man points to the horse and asks if he can buy it. Before accepting his offer, the owner asked the man, "What route did you take to get here?"

"The one with the big hill" responds the man.

"Well, I wouldn't take that route back if I was you. There is something funny with this horse. Whenever he's on top of a large hill, he will just sit there and it's impossible to move him. If yer gonna buy him, I'd take a different road home".

The man buys the horse and thanks the owner. Heeding his advice, he takes a detour home through the woods. All is going well and the horse rides a dream. However, they get to a shallow stream and in the middle of crossing the stream, the horse stops and sits down, refusing to budge. The man tries everything he can to get the horse to move but to no avail. Puzzled, the man walks back to the marketplace where he bought the horse and quizzes the owner:

"That horse I bought, well I was riding it through the woods and all was going fine until we got to this stream and whilst crossing it, the horse just sat down and now it won't budge. Do you know why?"

"Well" the owner responds, "there's something I forgot to mention; he sits on fish as well."