Coral reefs are massive calcareous rock structures that are slowly secreted by simple colonial animals that live as a thin layer on the rock surface. The living organisms continually build new structures on top of old, extending the reefs seaward toward deeper water and upward toward the surface.
The Florida Reef Tract comprises coral reefs along the southeastern edge of the Florida Peninsula in the Atlantic Ocean to the Florida Keys and westward into the Gulf of Mexico. In addition to the reefs themselves, coasts in these areas consist of calcareous beach sediments derived from pulverized corals.
Coral coast are also found throughout the Hawaiian Archipelago. Reefs grow adjacent to the volcanic island and provide beach sediments in a similar fashion to those along the Atlantic and Gulf coral coasts. In the remote and uninhabited Northwestern Hawaiian Islands, one of the world's most undisturbed coral reef ecosystems thrives among the islands and atolls.