Sandspit is formed through the process of longshore drift. Through traction and saltation, eroded materials are transported by waves to the coastline. The material is deposited on the coastline in a zigzag manner by waves. The waves swash the material up the coastline at an angle and backwash it down the beach at a right angle (Madricardo & Rizzetto, 2018). However, the swash angle is determined by the prevailing wind. Moreover, the prevailing wind determines the shape and growth of the sand spits.
Beaches are formed by deposition produced by wave processes and longshore drifts composing together sand, shingles and pebbles. Gently sloping beaches are formed through strong destructive waves that backwash more material away from the beach than up the beach (Madricardo & Rizzetto, 2018). Steeply sloping beaches are composed by constructive waves that push more material to the beach than they wash away.
Madricardo, F., & Rizzetto, F. (2018). Shallow coastal landforms. In Submarine geomorphology (pp. 161-183). Springer, Cham.