Q: What did the water say to the boat?
A: Nothing, it just waved.
Explanation: “Wave” is what you do when you move your hand as if saying hello. “Wave” is also the name for a way the top of the water moves: the raised part of the water that moves toward the shore is a wave. This joke plays on the word “wave” and is funny because the water waves (as if saying hello) while the water has waves (the raised part of the water).