The waves can also breach the bar by overwashing and eroding it. If the amount of water behind the bar is large, then release of this water can be very forceful and create a danger to persons in the area. Although terrestrial geologic processes do operate at the shoreline, the thing that distinguishes coastal geology is the dominant role played by waves as a geologic agent. Most of the waves you see are generated by the wind. In terms of the energy expended against the shoreline, the most significant waves are generated by storm winds.
Waves tend to come in two distinct varieties.
One type of wave is know as a sea. These are waves which are produced by local storms. They tend to be very chaotic and include a broad range of wave heights. The other type of waves are know as swell. These are waves produced by distant storms.