The Florida Keys National Marine Sanctuary is a U.S. National Marine Sanctuary in the Florida Keys. It includes the Florida Reef, the only barrier coral reef in North America and the third-largest coral barrier reef in the world. It also has extensive mangrove forest and seagrass fields. The Florida Keys National Marine Sanctuary, designated on December 28, 1990, was the ninth national marine sanctuary to be established. The Florida Keys National Marine Sanctuary protects approximately 2,900 square nautical miles of coastal and ocean waters from the estuarine waters of South Florida along the Florida Keys archipelago and the Hawk Channel passage, encompassing more than 1,700 islands, out to the Dry Tortugas National Park, reaching into the Atlantic Ocean, Florida Bay, and the Gulf of Mexico.