The Great Blue Hole
A perfectly round, deep-blue hole in a Caribbean reef holds stalactites from a time when it was dry land.
What was reported
The Great Blue Hole is a round sinkhole about 300 metres across and more than 120 metres deep, in the middle of Lighthouse Reef off Belize. From the air it looks like a dark blue eye in the turquoise water.
Jacques Cousteau brought his ship Calypso there in 1971 and called it one of the world's great dive sites. Divers found stalactites hanging from ledges far below the surface.
Explanations offered
It formed as a limestone cave during the ice ages, when the sea was much lower; the roof later collapsed and the sea flooded in. Stalactites only grow in air, which shows it was once dry. Expeditions have found that its deepest water holds no oxygen.
- When
- Explored from 1971
- Where
- Lighthouse Reef, Belize
- Witnesses
- Divers, including Jacques Cousteau
- Status
- Explained
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