great blue hole

The Great Blue Hole is a large submarine sinkhole off the coast of Belize. It lies near the center of Lighthouse Reef, a small atoll 70 km (43 mi) from the mainland and Belize City. The hole is circular in shape, over 300 m (984 ft) across and 124 m (407 ft) deep

Belize, is a country located on the northeastern coast of Central America. It is the only country in the area where English is the official language, although Kriol and Spanish are more commonly spoken. Belize is bordered on the north by Mexico, to the south and west by Guatemala and to the east by the Caribbean Sea. It's mainland is about 290 km (180 mi) long and 110 km (68 mi) wide.