common coastal features
Area where the land meets the sea; its features vary depending on climate, wind, sea and the type of rocks of which it is composed.
cave 
Natural underground cavity that results from the slow dissolution and erosion of rock by water.
sand island 
Exposed summit of a sand deposit formed near or occasionally far from a shoreline.
river estuary 
Mouth of a river that is influenced by the tides; it forms an indentation in the coastline that varies in width and depth.
lagoon 
Shallow expanse of seawater separated from the sea by a ridge of sand or a barrier island.