Walking on Water

A rabbi, priest, and a minister are out fishing in a boat on a big lake when the priest realizes that he has to go to the bathroom. Not wanting to disturb the fishing of the others in the boat by having them take him to shore, he gets out of the boat and walks across the water to do his business and then returns to the boat.A little while later the minister has to go also and he does the same. He walks across the water, does his business and returns across the water to the boat.
Finally the rabbi feels the urge to go to the bathroom too, so he climbs out of the boat. But instead of walking across the water, he falls into the water and starts to wildly splash around. The priest and the minister finally drag the rabbi back into the boat and the priest turns to the minister and says, "Maybe we should have told him where the rocks were."