This question was not popularly answered and the few candidates who attempted the question failed and they misunderstood coastal wave for coastal features. Coastal waves are swells of undulating water surfaces formed by the impact of winds which blow across coastal waters.  
The Processes of coastal wave erosion are:
Abrasion/Corrasion: The wearing down of the base of cliff/headland using the impact of the materials carried along by waves.                                             
Attrition: The wearing down of the load of the waves such as pebbles and other rock debris by robbing against each other, hereby disintegrating the materials into smaller particles.                                                                                 
Hydraulic action: The wearing down of cliff/headland through the impact produced by the sheer force of the waves against obstacles along the coast                      
Solution: The wearing a way of cliff/headland by the   dissolution effect /chemical action of the wave on soluble rocks, along the coast .e.g. coast made up of limestone or corals.           
Characteristics of coastal caves are:
            -           feature of marine/coastal erosion
            -           it is arch shaped
            -           may contain a blow hole or geo
            -           when two caves join they form an arch
            -           when the roof of the cave collapses a stack is formed
-           examples includeFingals caves in Scotland; Flamborough Head in Yorkshire (UK); Komenda caves and Kpone caves in Ghana