These are fringing reefs, barrier reefs and atolls . The main difference between each type of reef is the distance it lies from the beach shoreline. Fringing reefs grow near the beach shoreline . The space between the fringing reef and the shoreline is called the reefflat . During high tide the reef flat is usually covered with ocean water, but during low tide, the reef flat is usually exposed.
Corals grow best on the edge outside of the reef facing the open ocean.
This edge is called the reef front . Barrier reefs grow further away from the beach shoreline. In the ocean water between the barrier reef and the shoreline lies a protected, calm and often shallow, pond-like body of water called a lagoon. Barrier reefs also have a reef flat covered with ocean water during high tide, but has little or no water on it during low tide. Many corals grow on the outer reef front but they also grow well in the lagoon.