The principal agents of erosion of the littoral remain waves, tidal effects and marine currents. The masses of moving water act like "bumper collisons" that alter the rock.
One should not underestimate the importance of chemical degradation of the rock by spray (causing dissolution of material), as is the case for calcereous rock.
The form of the littoral depends on a great many parameters. It could be something like simple beaches composed of sand or pebble beaches, or it could be a matter of cliffs that have been fashioned by successive rockfalls.