They of course will say you broke the pencil. Ask them how they know. They heard it. Discussion should lead to idea of energy waves traveling away from break in all directions, impacting on each of their eardrums. Wait until water is still, then drop pebble into water.
Waves move out in all directions from the source of the disturbance.
The water waves move out from the source in all directions on the water's surface. The waves hit the nearer sides first, obviously taking longer to travel a greater distance. It is like this on Earth. Seismograph stations, where instruments are set up to record the arrival of earthquake waves, which are closer to the earthquake focus will record earthquake waves before stations which are farther away. By knowing the velocity of earthquake waves, geologists can calculate the distance the station is from the earthquake.