Great Blue Hole (Belize)

The Great Blue Hole lies within Lighthouse Reef Atoll in the Caribbean Sea, roughly 40 miles (about 64 kilometres) offshore from mainland Belize. It is a near-circular marine sinkhole, almost 1,000 feet (about 300 metres) across and more than 400 feet (about 120 metres) deep. The surrounding shallow reef creates a striking contrast with the hole’s dark, deep water.

The hole is the remnant of a large limestone cave that formed when sea levels were lower and later became flooded as the sea rose. Submerged formations, including ancient stalagmites, preserve evidence of its cave origins. These features make the site a record of past geological and sea-level changes as well as a dramatic underwater landscape.

Lighthouse Reef is one of the offshore atolls in Belize’s extensive reef system. UNESCO’s Belize Barrier Reef Reserve System includes the Blue Hole Natural Monument among its seven protected areas and was inscribed on the World Heritage List in 1996. Coral habitats and marine wildlife characterize the surrounding region; the UNESCO-listed system also includes habitats for threatened animals such as marine turtles and manatees.

The Great Blue Hole is known for diving, but its deep central waters are distinct from the shallow reef areas around its rim. The site has also drawn scientific exploration, including underwater surveys that documented its submerged cave formations. Because it is offshore and exposed to open-water conditions, reaching it typically requires a boat journey; nearby sections of Lighthouse Reef and Half Moon Caye offer other reef and island environments.