Orange Coral Photograph by Tim Laman A tubastraea coral waves its wispy, orange tentacles near Sangeang Island, Indonesia. Coral reefs cover less than one percent of the ocean floor, but they support one out of every four marine creatures.
Coral reefs are underwater structures made from calcium carbonate secreted by corals. Coral reefs are colonies of tiny living animals found in marine waters that contain few nutrients. Most coral reefs are built from stony corals, which in turn consist of polyps that cluster in groups.