Explanation:

 · Sea waves continuously strike at the rocks. Cracks develop overtime they become larger and wider. Thus hollow like caves are formed on the rocks. They are called sea caves. As these cavities become bigger and bigger only the roof of the caves remain thus forming sea arches. Further erosion breakes the roof and only walls are left. These wall life features are called stacks. The steep rocky coast rising almost vertically above sea water is called sea cliff.