I like this one: A man approaches a flooded river in his car. He sees a man fishing, and asks if he can make it across the river in his car. The fisherman replies, sure, it's not that deep. So the driver attempts to drive across the water, but his car rapidly starts to sink. The man abandons his car, and barely makes it to the shore. Sputtering and coughing, he starts berating the fisherman for telling him it was safe to cross.
The fisherman replies, "I don't understand, it only comes up halfway on the ducks."