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Quick answer — facts about the Great Blue Hole: It’s a nearly circular marine sinkhole inside Belize’s Lighthouse Reef Atoll, roughly 318 m (1,043 ft) across and 124 m (407 ft) deep, formed when Ice-Age cave systems flooded as sea level rose. It’s part of the Belize Barrier Reef UNESCO site.
TL;DR: If you’re after facts about the Great Blue Hole, here are the essentials: ~318 m wide, ~124 m deep, glacial-era origin, located within Lighthouse Reef Atoll and protected as part of Belize’s UNESCO-listed reef. Best views by scenic flight; advanced divers only for the vertical descent.
The Adventure begins
“We can’t go to Belize without seeing the Blue Hole,” is pretty much the way my friend summed up her opinion about our upcoming trip. We were eager to uncover any captivating facts about the Great Blue Hole. Our group of five girl friends was booked on a kayaking and snorkeling adventure with Island Expeditions, which would see us explore South Water Caye, Glovers Reef and Tobacco Caye. But the plan had us some distance from Lighthouse Reef, the area where the Blue Hole is located. Since we had added three days to chill out on Caye Caulker, prior to joining the tour departing from Dangriga, we decided to charter a plane to fly over it on the way.
Getting to the Blue hole: By air or by sea?
There are two ways to see the Blue Hole in Belize: from above in a plane or helicopter, or at sea level by boat where you can dive it. Diving tours do depart from Caye Caulker, but it’s an all-day outing, and restricted to licensed and experienced divers only. Check out this Blue Hole & Turneffe Islands helicopter tour departing from Belize City.
Chartering a flight
Our charter was with Maya Island Air. Our pilot Kenny picked us up like rock stars, from the airstrip located at the southern tip of Caye Caulker. Flying out over the coastline, ocean and various reefs presented an endless pallet of aqua-blues. We were all eyes, with good views, but I was grateful to accept the co-pilot seat for having arranged the booking. The flight to Dangriga, with a tour where some of the most interesting facts about the Great Blue Hole could be seen, took about 1.5 hrs. Scheduled group tours from Caye Caulker take about the same amount of time, but you are subject to their flight schedule coordinating with your plans.
How did the Blue Hole form?
The Blue Hole in Belize is basically a giant marine sinkhole. It was formed at the end of the last ice age when rising sea waters flooded a series of enormous caverns. The caves first formed 153,000 years ago, and were completely submerged 15,000 years ago. The Blue Hole feature was formed when sea levels were much lower, and at one time, it was actually above ground.
Where is the Blue Hole in Belize?
The Blue Hole is surrounded by the Lighthouse Reef Atoll. This coral atoll has an inner ring of shallow light-colored water that forms a ring for the deeper sapphire blue waters of the deep-water cave. The walls of the cave contain stalactites and stalagmites up to 12 meters (40 feet) in length. The presence of stalactites help confirm the theory that the formation was previously above sea level.
Essential facts about the Great Blue Hole (size, depth, location)
In addition to admiring the striking natural beauty of the Great Blue Hole, here are 15 fun facts about the Great Blue Hole:
1. Perfectly circular
The Blue Hole is perfectly circular at 300 meters (984 feet) across and 108 meters (354 feet) deep.
2. Largest sea hole in the world
While the South China Sea has the deepest sea hole in the world, named the Dragon Hole, at 300 meters (987 feet) deep, it is not the widest. There is another sea hole called Dean’s Blue Hole in the Bahamas, but no other is as large as the Blue Hole in Belize.
3. Jacque Cousteau documented it in 1971
Arguably the world’s most famous diver, Jacque Cousteau first brought attention to the Blue Hole, after which it has become a mecca of sorts for experienced divers.
4. Ranked #1 amazing place on Earth
According to the Discovery Channel, the Blue Hole is the #1 Most Amazing Place on Earth. Who are we to argue?
5. A World Heritage Site
The Belize Barrier Reef Reserve System was inscribed into the Unesco World Heritage Site in 1996. The designation protects seven areas, including the Blue Hole Natural Monument.
6. The second largest barrier reef in the world
The Blue Hole is located within the vast barrier reef off the shores of Belize. The reef second in size only to the Great Barrier Reef of Australia.
7. Charles Darwin visited
Ok, so it was a while back, but in 1836 Charles Darwin visited the Belize Barrier Reef and declared it the “most remarkable barrier reef in the Caribbean.”
8. Experienced divers only
Only Open Water Certified divers with a minimum of 25 logged dives are allowed to dive the Blue Hole. PADI certification is accepted worldwide. The depths reached demand skill and experience to navigate safely. Even at that, in 2018 when two submarines descended into the Blue Hole in an attempt to map its interior, they discovered the bodies of two divers at the bottom, out of three believed to have gone missing while diving there. The number of Blue Hole fatalities is not accurately recorded. However, one source estimates 130 divers died during the period of 1997-2012, and averaged eight per year. Another source claims as many as 200, which apparently includes a few snorkelers, unrelated to the depths reached. For some people, diving the world’s deadliest site is a challenge to embrace. Like I said earlier, the plane ride and view from above was awesome!
9. What’s at the bottom of the Blue Hole in belize?
Locals joke that there are two things at the bottom of the Blue Hole: sharks and GoPro’s. I guess in light of #8, we should add a third: bodies.
10 The dive is short, but the memories endless
Divers go to a depth of 130’ in their accent into the cave of the Blue Hole. As a result, the length of the dive is about 25 minutes, due to the depth and requirements to resurface safely. For the massive anticipation credited to the activity, the brevity of the dive comes as a surprise to some.
11. Accessible
The Belize Blue Hole is located 100km (62 miles) offshore of Belize City, within the Lighthouse Reef, a natural coral atoll. While it’s not exactly a short boat ride from the city, it is one of the more accessible sea caves in the world.
12. Who named the Blue Hole?
British diver Ned Middleton named the blue sea cave in Belize the “Great Blue Hole” in his book “Ten Years Underwater” published in 1988. While it’s certain the Spanish charted the waters initially, there doesn’t appear to be a recorded name they gave to the feature. Some have credited Jacque Cousteau with the name, when he first dove the location in 1972, but this is in fact not true.
13. Skydive the Blue Hole
Yes, you can skydive from a plane and then descend into the Blue Hole. It’s been done, and there is photo evidence on Instagram to prove it. The group shot with sky divers linking arms in a circle, and the Blue Hole in the middle is pretty cool. I’m sure there’s a video out there too!
14. Rare plant life
There are over 500 rare forms of animals and plant life found in the Blue Hole of Belize.
15. The Blue Hole gets lots of visitors
Each year, more than 200,000 people come to visit the Great Blue Hole from all over the world. Of course those numbers include both by sea and by air, but it’s an impressive number attracted to this unique ocean formation.
Our group was grateful for this once-in-a-lifetime experience in Belize, enriched by the amazing facts about the Great Blue Hole we learned along the way. It was a fine way to shake off Covid travel restrictions, and get out there to see the world again!
If you go
Flights can be booked through Maya Island Air and Tropic Air. In addition to scheduled group flights, private charters can also be arranged. With the exception of private or chartered vessels, the only other way to access the Blue Hole is to join a dive tour group. Belize Diving Services, Big Fish Dive Center and Frenchie’s Diving Services are a few of the operations you might want to check out. All were highly recommended in the Belize Lonely Planet guide book. Keep in mind the dive certification qualifications required to join a trip. Apparently, snorkelers can also join dive trips, but spots may be limited due to diver demand. And costs are likely to remain the same whether you dive or not, since a tour spot has been otherwise occupied.
Check out these day trips & tours to round out your Belize experience
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More Belize Adventures
We hope you found the fun facts about the Great Blue Hole as interesting as we did. Check out these articles for more Belize travel inspiration!
25 Things to See and Do in Caye Caulker
Island Expeditions Belize Kayaking Adventure
FAQ
It’s a nearly circular marine sinkhole inside Belize’s Lighthouse Reef Atoll, roughly 318 m (1,043 ft) across and 124 m (407 ft) deep. Formed from flooded limestone caves after the last Ice Age, it’s part of the Belize Barrier Reef UNESCO World Heritage site.
The best-cited dimensions are about 318 m/1,043 ft in diameter and about 124 m/407 ft deep. Day-to-day measurements can vary slightly depending on method and source.
Near the center of Lighthouse Reef Atoll, roughly 70–80 km (45–50 miles) offshore from mainland Belize. Most boat trips depart from Caye Caulker or Ambergris Caye (San Pedro).
During the last Ice Age, parts of the reef area were dry land with limestone caves. As sea levels rose, the caves flooded and collapsed in places, creating the sinkhole. Stalactites found deep inside confirm this origin.
Yes. It sits within the Belize Barrier Reef Reserve System, a UNESCO World Heritage site inscribed in 1996 that protects several reserves, cayes, and atolls (including Lighthouse Reef).
Requirements vary by operator. Many request Advanced Open Water (or equivalent), recent deep-dive experience, and often a checkout dive. Depth, overhead environments, and potential narcosis mean it’s best for experienced divers. Non-divers usually opt for scenic flights or rim-snorkeling.
Expect dramatic overhangs, caverns, and stalactites at depth. Marine life can include reef sharks and pelagics, but the most colorful coral and fish are typically on the surrounding Lighthouse Reef sites rather than deep inside the hole.
A scenic flight (from Belize City, San Pedro, or Caye Caulker) gives the iconic overhead view in under an hour. Boat snorkel trips let you experience the reef rim and nearby sites if you prefer to be on the water.
Belize is year-round, with dry season (roughly Nov–May) offering more stable weather. Trips depend on sea state and visibility, so always check local conditions and forecasts.
It’s a deep, technical environment. Below ~30 m/100 ft light fades, narcosis can set in, and overhead spaces exist. Go with a reputable operator, stay within your training, and follow the briefings. If you’re unsure, choose a scenic flight or shallow reef dives instead.
From San Pedro or Caye Caulker, expect roughly 2–3 hours each way, depending on boat, sea conditions, and stops at nearby sites. Operators based closer to Lighthouse Reef may be faster.
It’s one of the world’s largest by width, but other blue holes are deeper. Its combination of size, geological history, and dramatic setting is what makes Belize’s Blue Hole so famous.
Mary Charleson
Mary Charleson is a travel writer and marketing/media strategist for 50+ adventure travellers. She publishes Carryonqueen.com and FiveMinuteMarketing.com. In 2025, Carryonqueen.com earned 2nd place for Best Self-Published Travel Website (Travel Media Association of Canada). Mary also speaks to tourism leaders about modern marketing and inspires audiences to explore.