From the Florida Keys National Marine Sanctuary website: 

Designated on November 16, 1990, Florida Keys National Marine Sanctuary is one of 14 marine protected areas that make up the National Marine Sanctuary System. Administered by NOAA, a federal agency, and jointly managed with the State of Florida, Florida Keys National Marine Sanctuary protects 2,900 square nautical miles of waters surrounding the Florida Keys, from south of Miami westward to encompass the Dry Tortugas, excluding Dry Tortugas National Park. The shoreward boundary of the sanctuary is the mean high-water mark, essentially meaning that once you set foot in Keys waters, you have entered the sanctuary.

Within the boundaries of the sanctuary lie spectacular, unique, and nationally significant marine resources, from the world’s third largest barrier reef, extensive seagrass beds, mangrove-fringed islands, and more than 6,000 species of marine life. The sanctuary also protects pieces of our nation’s history such as shipwrecks and other archeological treasures.

With the designation of Florida Keys National Marine Sanctuary, several protective measures were immediately put into place, such as prohibiting oil exploration, mining, or any type of activity that would alter the seafloor and restricting large shipping traffic. Also, anchoring on, touching, and collecting coral were all restricted within sanctuary waters.

The passage of the Florida Keys National Marine Sanctuary and Protection Act in 1990 also called for the development of a comprehensive management plan. A set of public scoping meetings, followed by a series of workshops, collected input from federal, state, and local interests holding knowledge of sanctuary problems. These meetings, workshops, and extensive public input laid the foundation for the sanctuary management plan that was ultimately implemented in July 1997.

Today, Florida Keys National Marine Sanctuary protects 2,900 square nautical miles of waters using an approach that addresses the variety of impacts, pressures, and threats to the Florida Keys ecosystem. The sanctuary is administered by NOAA and is jointly managed with the State of Florida.