A tidal pool is a pool of water remaining after the tide has gone back out. It is also referred to as a tide pool or a rock pool. They can be small and shallow or large and deep. The small ones are generally found far back on the seashore, and the larger ones are closer to the sea. Tide pools are formed when a high tide comes in over a rocky seashore. Water fills depressions in the ground, which get converted into secluded pools as the tide retreats. This procedure, recurring twice a day, refills the seawater in what otherwise might become a stagnant pool.