These reefs are found adjacent to shores in shallow waters. They are formed from separate corals growing together in shallow water. As they increase in size and number they grow further towards the open water. The water condition is more favorable since there is no debris from the land being deposited in the vicinity of the reef. The second type of reef is known as a barrier reef.
Barrier reefs consist of a line of single reefs running parallel to a coastline.
The reef is separated form the mainland by an expansive lagoon. The outer seaward edge of the reef slopes rapidly to a great depth. The outer edge of the reef has a massive expanse of coral growing just beneath the surface containing huge boulders and pinnacles which extend seaward under the breakers to form a steep rough cliff. This cliff merges beneath the active zone of reef formation into a slope of dead coral, which is known as the talus slope. Behind the main platform of the reef there are crevices and gullies filled with fragments of rock, coral and sediment which forms a crude cement and gives a base for the coral to grow upon.