Tie pools (also tidal pools, rock pools or rock and roll pools) are rocky pools by oceans that are filled with seawater. Tide pools can either be small and shallow or deep. The small ones are usually found far back on the shore and the large ones are found nearer to the ocean. Tide pools are formed as a high tide comes in over a rocky shore. Water fills depressions in the ground, which turn into isolated pools as the tide retreats. This process, repeated twice a day, replenishes the seawater in what otherwise might be a stagnant pool.