http://coris.noaa.gov/portals/florida.html Florida NOAA's Coral Reef Information System] Accessed December 14, 2010 It lies a few miles seaward of the Florida Keys, is about 4 miles (6 to 7 km) wide and extends (along the 20 meter depth contour) 270 kilometers from Fowey Rocks just east of Soldier Key to just south of the Marquesas Keys.