Great Blue Hole
Belize
The Great Blue Hole is a large, circular marine sinkhole located near the center of Lighthouse Reef, about 70 km from Belize's mainland. Measuring 318 meters in diameter and 124 meters deep, it covers a surface area of approximately 70,650 square meters. This natural wonder formed during multiple phases of Quaternary glaciation when sea levels were significantly lower, with stalactite analysis dating its formation to 153,000, 66,000, 60,000, and 15,000 years ago. As ocean levels rose, the cave system flooded, creating the sinkhole seen today. It is part of the Belize Barrier Reef Reserve System, a UNESCO World Heritage Site, underscoring its ecological and geological importance. The site gained worldwide fame when Jacques Cousteau declared it one of the top five scuba diving sites globally, highlighting its unique underwater formations and rich marine biodiversity. Expeditions have mapped its depths and cave systems, revealing geological tilting and anoxic layers that create distinct underwater environments. The Great Blue Hole continues to attract adventurous divers and marine scientists, offering a rare glimpse into karst limestone formations and underwater ecosystems.
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Tip: The best time to visit the Great Blue Hole is during the dry season, from late November to mid-April, when the seas are calmest. Advance booking of diving tours is recommended due to high demand and safety requirements. Certified divers should ensure they have cave diving qualifications for deeper explorations. Visitors can benefit from package deals offered by local operators, and it is advisable to check weather and sea conditions before planning a trip. Respect for the natural environment and adherence to safety protocols are essential when diving here.
Interesting facts
- •The Great Blue Hole is approximately 318 meters wide and 124 meters deep, making it one of the largest marine sinkholes in the world.
- •Jacques Cousteau declared it one of the top five scuba diving sites worldwide and conducted significant explorations there in 1971.
- •The sinkhole's formation involved multiple glaciation periods, with stalactites found underwater dating back over 150,000 years.
- •A 2018 submarine expedition mapped the interior using sonar and discovered an anoxic layer of hydrogen sulfide about 91 meters deep.
- •The bodies of two missing divers were found at the bottom during the 2018 expedition and respectfully left undisturbed in the sinkhole.
History
The Great Blue Hole formed over several glaciation periods during the Quaternary era, with stalactites indicating formation phases at 153,000, 66,000, 60,000, and 15,000 years ago.
Initially a dry limestone cave system, it flooded as sea levels rose, creating the current marine sinkhole.
Jacques Cousteau brought global attention to the site in 1971 by exploring and mapping its depths.
Further scientific expeditions in 1997 and 2018 expanded understanding of its geology and underwater environment, including the discovery of anoxic layers and submerged cave systems.
Place Guide
Blue Hole Dive Site
The primary attraction is the dive site itself, featuring dramatic vertical walls, underwater stalactites, and diverse marine life including reef sharks and giant groupers. The site offers multiple ledges at varying depths for exploration.
