A place I'd like to one day see.

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.[1] It was formed during several episodes of quaternary glaciation when sea levels were much lower. Analysis of stalactites found in Great Blue Hole shows that formation took place 153,000; 66,000; 60,000; and 15,000 years ago.[2] As the ocean began to rise again, the cave was flooded.[3] The Great Blue Hole is a part of the larger Belize Barrier Reef Reserve System, a World Heritage Site of the United Nations Educational, Scientific and Cultural Organization