The Great Blue Hole is a giant marine sinkhole off the coast of Belize. It lies near the center of Lighthouse Reef, a small atoll 70 kilometers (43 mi) from the mainland and 300 kilometers (186 mi) east of Belize City. The hole is circular in shape, over 300 meters (984 ft) wide and 124 meters (407 ft) deep. It was sculpted during the Pleistocene g