For example, if the waves appoach the shoreline from the south, longshore current moves from south to north. But longshore current and the resulting transport of sediment is only one of the dynamic processes that constantly alters the shoreline. As waves repeatedly hit the shore, water moves onto the beach and then retreats in a continuous cycle. However, the waves are not all that moves on the shoreline. In fact, the sediment on the shore is also always on the move.
Great energy is expended on the beach as waves crash against the shoreline.
This energy allows the water to transport sediment. The grains are lifted as the waves in the swash zone move onto the beach, and then the grains are deposited again as the water retreats. In this case, no real net movement of sand occurs in the swash zone. However, waves generally do not form parallel to the shoreline, and thus, usually approach the shore at an angle. Consequently, beach sand will have a net movement up or down the beach, depending on the direction of incoming waves.