A spit is a depositional coastal landform that forms by longshore drift. The prevailing wind pushes constructive waves up the beach at an angle as the swash. The waves then travel at a ninety degree angle back down the beach due to gravity as the backwash. Sediment is pushed up and dragged back down the beach in this way through the process, longshore drift. This process continues down the entire beach, leading to mass transportation of sediment, until the mainland ends. At this point, sediment is deposited and builds up causing an extension of the mainland out into the sea as a spit. Spits can form a recurved hook as to secondary winds cause sediment deposition to occur at a different angle than previously. A salt marsh can form behind a spit if an estuary is present due to the mixing of fresh water, salt water and sediment.