A beach is made of very small loose rock (sand) that gathers at the shore of a body of water. Beaches are created by waves or currents. The sand comes from erosion of rocks both far away from and near the water. Coral reefs are a major source of sand.

A beach's shape depends on how the waves move. Some waves move material up the beach, while others move it down the beach. On sandy beaches, the waves move sand away from the beach, making gentle slopes.

When the waves are not strong enough to move the sand away, the beach is steeper.

Crabs, insects, and birds feed on material left by the waves. Some small animals dig into the sand to get their food. Birds use beaches to nest, and sea turtles lay their eggs on ocean beaches. Sea grasses and other beach plants grow on areas of the beach and dunes where there is not much activity.