The destructive force of water is increased manifold when the water contains various rock fragments. Fragments of rocks picked up by the water are hurled against the shore as the wave breaks.
The impact of large rock fragments thrown by large waves is capable of breaking up the most resistant rocks like granites and massive sedimentary ones, while the loosely consolidated rocks exposed along the shore are rapidly worn down by the impact of sands, gravels and pebbles by the waves.
Besides, the rock particles due to their back and forth movement over the bed rocks give rise to continuous rubbing and grinding (which has been likened to the effect of saw acting at a cliff-foot) wears down the bedrock lying along the shore.
This process of wear and tear is known as abrasion. Abrasive action is faster and conspicuous where the rocks are soft and much jointed and slow where they are hard and strong.