Remnants of the Ice Age, blue holes are otherworldly geological underwater formations created by Mother Nature after rising sea levels filled sinkholes with water. Extremely deep with networks of caverns, these kinds of profound voids are even visible from above due to their dark navy hue - a shade that has come to define their existence.

There are a number of famous blue holes all around the world, with most playing host to incredible topography and diverse marine fauna and flora, making them prolific sites of importance for research, as well as snorkeling, and scuba diving, and freediving. The hole sitting in second place on the chart of the planet's deepest is the mesmeric Dean’s Blue Hole in the Bahamas, which has rightly earned its crown as one of the most breathtaking - and daring - dive sites on Earth.

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Thanks to its crystal clear water and intense depths, diving at Dean's Blue Hole, like many of the most mind-boggling dive sites ever discovered, is a once-in-a-lifetime opportunity - and there are many points to take into account if one wants to make the most of the experience, as well as explore it properly and safely. From fascinating facts and geological history to diving, safety, and certifications required, this guide answers all the burning questions adventurers may ever ask before gallivanting off to explore the second deepest, darkest subsea hole the world has ever seen.

What Is A Blue Hole?

A blue hole is a vertical cave - a term assigned to a sinkhole filled with deep blue water. The color is the result of a combination of transparent water and bright white sand, and the deeper one goes, the bluer it gets; of all the colors in the light spectrum, red, yellow, then green all become absorbed as they penetrate through the water, leaving blue the only one to make it to the deepest levels of the hole.

How Are Blue Holes Formed?

Blue holes owe their existence to the time when the sea level was far shallower than it is today. Many of these holes were formed by deeper groundwater, which gradually dissolved their limestone casing until their ceiling finally collapsed. Even after ocean levels began to raise post-Ice Age, these vertical holes in the sea would fill with water. Scientists believe that Dean’s Blue Hole probably formed in this way around 15,000 years ago, although research and discussions regarding its birth are said to be still ongoing.

How Big And Deep Is Dean’s Blue Hole?

Of all the blue holes around the globe, Dean's Blue Hole is the second deepest just behind Dragon Hole in the South China Sea - although this remains a topic of debate, for the latter isn't exactly a straight, vertical descent from the surface to the bottom. Additionally, Dean's is the second-largest blue hole next to Belize Blue Hole, which is notably bigger, but not deeper.

Located just off the coast about one kilometer from Clarence town on the Atlantic side of Long Island in the Bahamas, the natural splendor of Dean's Blue Hole can be marveled at from the staggering cliffs above and the pristine silken beach to its side; its imposing deep blue color set amidst its shallow turquoise lagoon and its neighboring beaming white sand beach all collectively create an exotic scene akin to an extra-terrestrial world.

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Dean’s Blue Hole starts off at a depth of around six meters before plunging down to a mind-boggling 202 meters (663 feet) towards the ocean floor, with its sheer walls dropping vertically all around its diameter. From the surface, its almost-circular shape boasts a diameter ranging from 25 to 35 meters (82 - 110 feet), but after descending around 20 meters (66 feet), it widens into an even larger cavern with an approximate diameter of about 100 meters (330 feet). At the very bottom, there's a real darkness, with rocks, sand, and other ocean titbits settled on the seabed. Because of such daunting depths (and the fact it's claimed lives), it's no wonder the hole is often referred to as the "divers’ tomb".

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How Deep Are Blue Holes In General?

Each blue hole is unique to the next, with every single one possessing its own characteristics, shapes, depths, and marine life ecosystems. Out of all the most noteworthy blue holes, the most popular in descending order of their depths are as follows:

  • Dragon Hole in the South China Sea: 300 meters (987 feet) - also known as "Longdong"
  • Dean’s Blue Hole: 202 meters (633ft)
  • The Belize Blue Hole: 108 meters (407ft)
  • Dahab Blue Hole: 120 meters (328ft)
  • Dwejra Blue Hole: 25 meters (49ft)

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What About Snorkeling, Scuba Diving & Freediving At Dean's Blue Hole?

Dean’s Blue Hole is a brilliant place for snorkeling, scuba diving, and freediving, and unlike other blue holes, it’s not situated far out at sea - but rather right at the edge of Long Island island, allowing convenient access. Plus, the shelter from its surrounding cliffs keeps ocean conditions irresistibly calm, translating to zero current, crystal clear visibility, and thus, excellent diving and snorkeling. And when coupled with the powder-white sand beaches and dramatic cliffs to its side, the site is also a perfect sunbathing and sightseeing spot should jumping in the water not be on the to-do list. But of course, to make the most out of a visit, people really need to dive in and get wet.

Intrepid blue hole explorers and wannabe Jaques Cousteaus will be delighted to know there are dozens of local dive and tour operators in the area offering snorkeling, scuba diving, and freediving trips to Dean's Blue Hole. One of the most reputable of the latter kind is Vertical Blue - a well-established freediving school running courses and excursions in Dean’s Blue Hole for both beginners and intermediates, as well as training camps for a more in-depth experience. What's more, this particular dive site is also the official location where the annual Vertical Blue freediving competition takes place, so lucky visitors who arrive at the right time might get to watch the world's top competitive freedivers doing what they do best - breaking world depth records.

What World Records Have Been Broken At Dean's Blue Hole?

As one of the world's most esteemed freediving destinations, Dean's Blue Hole attracts the most experienced, skilled, and courageous freedivers from all corners of the globe. First reached by Jim King in 1992, it has since become a prestigious site that's garnered the attention of earth's freediving elite.

After its popularity and celebrity catapulted the site to fame, professional diver William Trubridge broke a freediving world record here in April 2010, in which he descended to a depth of 92 meters on a single breath using only his feet for propulsion - not fins.

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On December 14, 2010, he broke his own record when he reached 101 meters, again without breathing while using only his hands and feet to swim. Unfortunately, in November 2013, another professional diver named Nicholas Mevoli died during his attempt to set a new record.

In more recent years, past records have since been smashed like never before. Russia’s Alexey Molchanov snatched the men’s world record in the Free Immersion discipline in 2021, performing a 126-meter (413 feet) descent in four minutes 45 seconds. For the girls, Alessia Zecchini from Italy broke the women’s world record in the Constant Weight (CWT) category with her 115-meter (377 feet) dive, which was quickly usurped by Slovenia's Alenka Artnik several minutes later when she descended to 118 meters (387 feet).

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How To Dive Dean's Blue Hole?

No matter which blue hole one adds to the itinerary, they're all reserved for experienced, confident divers with the appropriate certification level. Usually classed as a "technical dive", exploring blue holes - Dean's Blue Hole included - demands uncompromised diving skill, excellent buoyancy control, calm, and the ability to equalize the ears and airways with minimal problems due to the great depths.

Furthermore, it is of absolutely paramount importance that divers watch their air consumption, depth, and time spent underwater whilst diving into a blue hole; it's all too easy to get distracted by such beauty and awe, causing even seasoned divers with thousands of dives under their belt to forget about checking these things before realizing they've gone far too deep, gone beyond their time limits, and are low on air.

Whilst some operators in this part of the Bahamas do offer beginner scuba diving certification courses (such as the Open Water Certification) at the blue hole for non-certified divers, depth is limited to a maximum of 12 meters for the first two open water dives, followed by a maximum of 18 meters for the third and fourth dives when undertaking this level of certification - all which are the standards set by most dive education agencies around the world, no matter where a course takes place.

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How To Dive Deeper At Dean's Blue Hole?

Want to go deeper? Then an advanced diver certification will be needed. Those taking an advanced diver course will be able to descend up to 30 meters - after which upon completion they will be certified to dive this deep (another standard set by the professional dive education industry). Divers who want to dive even deeper will need to be deep diver certified already, or take a deep diver specialty course, which certifies them up to a maximum depth of 40 meters - the absolute limit that recreational divers are certified to.

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Naturally, because of how deep Dean's Blue Hole is and how dangerous it can potentially be to the unskilled, inexperienced, and nervous diver, it is strongly recommended that all divers - be they expert or not - scope out a reputable dive center that'll provide an experienced, qualified divemaster or instructor to lead the way throughout the trip. Several companies offer guided snorkeling, freediving, and scuba diving tours to Dean’s Blue Hole, although its easy accessibility means it is indeed possible to explore it by oneself - despite not being advised.

Ultimately, given they have the courage to plunge into a 202-meter (663 feet) underwater hole, most divers will be in their element here, perhaps even finding peace and tranquillity, which freediving inherently offers with its therapeutic effects - as leading dive training agency PADI explains. But alas, all diving entails risks, however with adequate confidence, tenacity, skill, certification, and training, diving Dean’s Blue Hole - as well as the many other blue holes peppered across the planet - is safe, albeit challenging for those with less experience.

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What Is There To See?

Dean's Blue Hole itself is the main show-stopping spectacle that all its visitors descend for. The topography, stunning rock formations, and vibrant corals are enough to fulfill a dream diving day alone. However, what some may not know is that the hole and its vicinity also contain myriads of marvelous marine species. Snorkelers who stick to the shallows can enjoy the most beautiful corals around the rim of Dean’s Blue Hole, along with lots of exotic subsea species thriving near the surface.

But scuba divers and freedivers who explore deeper can observe not only the hole's tremendous formations and depths, but also all manners of creatures large and small, including snapper fish, big groupers, tarpons, various rays, plentiful tropical fish species, huge shoals of schooling fish, and even smaller macro critters that like to bustle in the sandbanks - like shrimp and crabs.

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When Is The Best Time To Visit?

Dean's Blue Hole is perfect to visit all year round with some minor seasonal differences depending on the month. The heaviest rains occur in June, August, and September, which may reduce visibility a little. Because it's protected from the open ocean, there's no current no matter the weather or season, and snorkeling, diving, and freediving are available all year with superb visibility as the cherry on top. Furthermore, water temperatures average 24° C (75° F) from December to March, and 31° C (88° F) in the summer between June and August, thus thermally-challenged swimmers and divers should probably go during the warmer summertime.

How To Get There & Where To Stay?

There's more than one way to visit and stay if attending Dean's Blue Hole is on the cards. The hole is situated on Long Island's southern side and many hotels and local guides on and around the island offer tours and transport to the white-and-blue wonder most days. This means that those staying on the island or elsewhere nearby should have no trouble finding their way there no matter where they attend from.

A convenient option - one that involves actually staying for more than a day, not just for a day-long trip - is to stay on Long Island itself in Clarence Town where accommodation options are aplenty; small hotels and self-catering villas are what most people book. However, there are no fancy five-star resorts, which in all honesty adds to the island's small-world charm, and laidback vibe, and maintains its untouched scenery and seascapes unspoiled by tourism.

Despite being a common stop-off for vacationers on sailing trips, and the fact that one can stay in Clarence Town, it's also possible to visit Dean’s Blue Hole on day trips from Florida. The majority of visitors go by chartering a flight from Nassau airport to Deadman’s Caye Airport on Long Island, from which the hole is a mere 10-minute drive.

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Whilst both Bahamas Air and Southern Air operate flights to Long Island, it's important to note that some flights also stop at Stella Maris Airport on the island’s north side, so travelers should be careful not to get off the plane at the wrong airport. Should one fly into Stella Maris Airport instead, it's not the end of the world; the Dean's Blue Hole is only around an hour away by car or taxi - of which there is no lack of at the airport.

Overall, Dean's Blue Hole is undoubtedly among Mother Nature's most jaw-dropping wonders. It's a must-experience for all underwater enthusiasts - be they swimmers, snorkelers, scuba divers, or freedivers. Since it's very accessible year-round with numerous options to get there - along with ample accommodation on Long Island - there's no excuse not to tick this unparalleled natural formation off the bucket list.

As long as all safety precautions are taken, appropriate dive certifications are acquired, and divers prepare in advance for what might just be their most life-changing dive yet, there's no reason why Dean's Blue Hole has to be anything but tear-inducingly enjoyable. The only thing that's left to do? Buy a heckin' good camera and don't forget to bring it.

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