Deposition occurs when the sea loses energy and drops any matter that it may be carrying. Deposition is a coastal process.
In geography, deposition refers to the way that constructive waves are developed. When certain conditions arise, the sea cannot maintain it's energy and thus drops any materials it was carrying, such as sand, pebbles and other rock particles.
This may occur in several different locations, including areas such as a sheltered cove or a bay. Lack of wind may also cause a deposition. It can also be caused when waves enter a shallow area, or if there is too much material for the water to carry.