Waves like other agents of gradation such as, running water, wind, and glaciers do the work of erosion, transportation and deposition, and produce a variety of coastal landforms.
Currents in the oceans may be periodic or permanent and they also have their share in shaping the coastal landscape. However, the effect of the work of waves and currents is limited to the narrow zone where the land and water meet.
The line of contact between the land surface and the ocean surface is called the shoreline. The shore is divided into two zones i.e. the foreshore and the backshore. The foreshore extends from the lowest low-water line to the average high-water line.
The backshore, on the other hand, extends from the high-water line to the coast line. The coast or coastline is a broader term which refers to a zone in which coastal processes operate or have a strong influence.
The coast includes the shallow water zone in which waves perform their work, as well as beaches and cliffs shaped by waves, and coastal dunes. It may be pointed out that land- form changes are made both on the landward and seaward sides of the shoreline.
It is to be borne in mind that the shoreline is not fixed; its position undergoes a change with the tides, and with long term changes in the sea level and with diastrophic movements of the adjoining land itself.
The coastal zone comprises the area on land as well as areas submerged under water through which the shoreline changes with time.
However, during storms when the longest waves are produced, their gradational work is many times more than that by normal waves.
The main function of the waves that reach the coastal zone includes straightening and smoothening the shoreline. Bays and inlets are filled in, whereas the promontories and headlands are cut back by wave action.