Here's how:

* Wave Action: Waves crashing against the coastline wear away the softer rock, creating caves, arches, and eventually, sea stacks.

* Hydraulic Action: The force of the water itself, pounding against the rock, can break it down.

* Abrasion: The waves carry sand and pebbles, which act like sandpaper, grinding away at the rock.

Deposition (the process of dropping sediments) plays a role in the formation of other coastal features like beaches, spits, and sandbars, but not sea stacks.