Gray's Reef National Marine Sanctuary, Marine sanctuary off Sapelo Island, Georgia, United States

Gray's Reef National Marine Sanctuary covers 22 square miles of the Atlantic, 19 miles off Sapelo Island, Georgia. Beneath 60 to 70 feet of water lie rocky sandstone outcrops up to 2 to 3 metres tall, cut by ledges and crevices, alongside sandy flats. Invertebrates and fish coat the rock so densely that the stone disappears in places, giving the habitat its name, live bottom.

Gray's Reef was designated a National Marine Sanctuary in January 1981, protecting 22 square miles of live-bottom reef 19 miles off Sapelo Island. The seabed was dry land as recently as 8,000 years ago, and human occupation of the area dates back at least 13,250 years. A 2003 University of Georgia study by Ervan G. Garrison, Sherri L. Littman and Megan Mitchell reported Clovis and Paleoindian artifacts more than 10,000 years old.

The reef's name comes from Milton "Sam" Gray, a Sapelo Island resident and recreational fisherman who worked the area in the 1960s and reported the ledges to researchers. The site lies 19 miles off Sapelo Island, and its sandstone outcrops sit under 60 to 70 feet of water. Divers and anglers today know it as a live-bottom reef rather than a coral reef.

The reef lies 19 miles off Sapelo Island, submerged 60 to 70 feet (18 to 21 m) below the Atlantic, so it can only be reached by boat and seen by diving. Check wind and wave forecasts before departure, since surface conditions can make diving difficult or unsafe. Federal rules protect the sanctuary: removing specimens or disturbing the marine environment is prohibited.

Gray's Reef was dry land as recently as 8,000 years ago, when sea levels were over 200 feet lower. A 2003 University of Georgia study by Ervan G. Garrison, Sherri L. Littman and Megan Mitchell reported fossils and Clovis-culture artifacts from the site, evidence of hunters who camped there more than 10,000 years ago.