A sand wave is a lower regime sedimentary structure that forms across from tidal currents.
[1] Sand waves are formed through the action of the wind or water (through waves or tidal currents)[2] and are a product of unidirectional flow.
Sand waves are the result of a mean flow velocity between 40 and 70 cm/s.
Sand waves also form underwater.
[3][4] Media related to Sand waves at Wikimedia Commons