Andros Island is an archipelago within the archipelago-nation of the Bahamas, the largest of the 26 inhabited Bahamian Islands. Geo-politically considered a single island, Andros has an area greater than all the other 700 Bahamian islands combined. The land area of Andros consists of hundreds of small islets and cays connected by mangrove estuaries and tidal swamp lands, together with three major islands—North Andros, Mangrove Cay, and South Andros. The three main islands are separated by "bights", estuaries which trifurcate the island, connecting the island's east and west coasts. It is 104 miles (167 km) long by at its widest 40 miles (64 km) wide.
Noteworthy for a unique combination of marine features and ecosystems, Andros rests on the west side of the 6000 foot (3+ km) deep Tongue of the Ocean. The Andros Barrier Reef is the World's third longest after Australia's Great Barrier Reef and the Central American Belize Barrier Reef, runs for 142 miles (225 km) averaging a distance of only 1–2 miles from the Andros shore. The extensive flats of the Great Bahama Bank lie to the west, northwest and south of Andros. The island is home to the world's largest collection of Blue Holes.