Approximately 60 miles (100 kilometers) from Belize City, the almost perfectly circular Blue Hole is more than 1,000 feet (305 meters) across and some 400 feet (123 meters) deep.
The hole is the opening to what was a dry cave system during the Ice Age. When the ice melted and the sea level rose, the caves were flooded, creating what is now a magnet for intrepid divers. Today the Blue Hole is famed for its sponges, barracuda, corals, angelfish—and a school of sharks often seen patrolling the hole’s edge.
(Photograph published in "A Celebration of Reefs," August 2003, National Geographic magazine)