Odd things can happen when a wave meets a boundary. In the ocean, tsunami waves that are hardly noticeable in deep water can become quite large at the continental shelf and shore, as the waves slow and their mass moves upward. In a recent study led by School of Physics Dunn Family Professor Daniel Goldman and published in the journal Physical Review Letters, scientists have shown that a floating, symmetric oscillating robot will experience forces when it comes close to a boundary. These forces can be used for self-propulsion without the need for more typical mechanisms such as a propeller.