Tides are the displacements of water masses generated by variations in the forcesof gravity applied on the Earth by the Moon in rotation around the Earth. They produce vertical displacements of sea level, associated with variations in potential energy, and tidal currents, associated with kinetic energy. Tides are only significant in an ocean-sized basin, such as the Atlantic Ocean or the Pacific Ocean. In a lake or a sea, even as large as the Mediterranean Sea, the tides are of low amplitude.