Marathon, Florida, United States

Sombrero Reef

Sombrero Reef is the main outer-reef site for the Middle Keys, located about 4.5 nautical miles south of Marathon and inside a Sanctuary Preservation Area of the Florida Keys National Marine Sanctuary. The reef is marked by Sombrero Key Light, a screw-pile lighthouse first lit in 1858 and listed on the National Register of Historic Places. Underwater, the site is a spur-and-groove formation with profile from about 2 metres on the inner reef flat to 9 metres on the outer ledge. The shallow tops are heavily colonised by elkhorn coral, brain coral and branching gorgonians. It is a reliable spot to see large numbers of bluestriped and French grunts, blue tangs, midnight and stoplight parrotfish, hawksbill turtles, Caribbean spiny lobster and the occasional nurse shark. The shallow profile and good moorings make Sombrero ideal for open water students and snorkelers, while photographers like the broad sun-lit topography. Currents are usually mild but can run on the outer wall.