Hydraulic Action
Erosion caused by the force of water being compressed into the gaps of rock, causing them to break off
Abrasion
Erosion caused by water picking up small rocks and using them to help erode the coastline by 'scraping'. This is what's known as the sandpaper effect.
Attrition
Erosion where rocks smash each other making them smaller.
Corrosion (solution)
The erosion of land caused by chemical processes (e.g. acid rain). The sea is also natural acidic.