Put a small amount of water into a rectangular baking dish, and set it on top of an overhead projector. Make waves in the pan by tapping on the container. Observe the patterns of
the waves projected on a screen or wall. Test the effects of obstructions on waves by putting some obstructions in the pan to represent wharves or jetties. Make sure that your obstructions are heavy enough that they don't float - maybe some rocks. You will discover that waves seem to move around obstructions and that waves change direction after they strike a surface, thus producing a sheltered or calm area on the surface directly in front of an obstruction.