Some concepts related to waves, though, are difficult to demonstrate in the classroom. They require observing water waves on a scale that is not ordinarily feasible for the classroom teacher because the necessary equipment is not available. The teacher demonstrations presented here relate to these aspects of water waves that are normally difficult for students to observe. They were developed for a large wave tank and are designed for use in a classroom. In this Activity, you will use a large Plexiglas tank to help students understand wave reflection and interference, the relationship between wave velocity and depth, and the effect of the seafloor on the motion of water and sand.