Atolls

Atolls are reefs that are found far from any major land masses. If a land mass is a small island, it may disappear under the surface of the ocean. It then becomes an atoll. This is how an atoll is formed.

Atolls can also develop when patch reefs sink below the surface of the water.

Atolls are roughly circular or horseshoe shaped, and they surround a lagoon. The result is that there are several low coral islands surrounding a lagoon.

Atolls can survive in rough water.