Two fishermen are out on the lake in a boat they had rented at the dock.
After an hour or so, they drift over a deep hole and start catching fish faster than they ever had before in their lives.
This goes on for a while until one of them pulls a large piece of chalk out of his tackle box and draws a large "X" in the bottom of the boat.
"What did you do that for?" asks the other one.
"So we can find this spot again!" is the reply.
"That's the dumbest thing I ever heard," says his buddy."…How do you know we'll get the SAME boat next time?"