Apo Reef two lagoon systems, the north and south lagoons which are bounded by narrow reef platforms. It is a almost triangular northern and southern atoll-like reefs separated by a deep channel that is open to the west. The channel runs east to west from deep with a fine white sand bottom, numerous mounds and patches of branching corals under the deep blue water. The north lagoon is an enclosed triangular coral reef platform partly exposed during low tide. It is relatively shallow with depths of about . While the south lagoon is an inverted triangular coral platform enclosed on two sides
Florida Reef open ocean. Channels between the Keys allow brackish water from the bays to flow onto the reefs (especially in the middle Keys), limiting their growth. The Florida Reef consists of two ridges separated from the Florida Keys by the Hawk Channel. Closest to the Keys is a sand ridge called "White Bank", covered by large beds of sea grass, with patch reefs scattered across it. Further out to sea on the edge of the Florida Straits is the second ridge forming the outer reefs, covered by reefs and hard banks composed of coral rubble and sand. Almost 1,400 species of