The beach zone is derived from sand and gravel produced by the biological and physical erosion of reef limestone. Rocky intertidal areas may retain water in tide pools even at low tide. The organisms that live in tide pools are adapted to withstand intense ultraviolet radiation, desiccation and high salinities. Rocky intertidal areas may retain water in tidepools even at low tide. The organisms that live in tide pools are adapted to withstand intense ultraviolet radiation, desiccation, and high salinities.
Currents flow in and out of the lagoon through channels in the reef.
The channels also serve as corridors for roving predators, like jacks, which move from the outer reef to feed in the lagoon and goatfishes, which move from the lagoon to feed on the reef flat at high tide. The numbers on the cross section of the reef represent the zones. Select a zone from the list for more information. Reef Flat 3. Algal Ridge 4.