Wave energy. Computer simulation showing ray trajectories travelling at different speeds through a random, weakly deflecting medium in a three-dimensional plane. The rays are analogous to ocean waves and the deflecting medium act in a similar way to ocean eddies. The eddies act as an optic lens and cause refraction of the waves resulting in areas of concentrated energy. This is visible as a pattern of twisting and branching known as caustics. It is believed that caustics resulting from strong ocean eddies interacting with wave action may be the cause of giant ocean waves known as freak, or rogue waves. Such waves have been reported to reach as high as 30 metres and have been blamed for the disappearance of some ships. Simulation created by Eric Heller, Professor of Physics at Harvard University, Massachusetts, USA.