Created during ice ages as a result of limestone erosion and rising sea levels, blue holes feature on the bucket list of many divers.

Whether it’s the challenge of their vertiginous depths, the thrill of the unknown, or simply the unique experience of witnessing a geological phenomenon firsthand, countless divers travel from all over the world to visit blue-hole dive sites each year. Here we’ll take a look at three of the world’s top three blue hole dive sites, and at what divers can expect should they visit.

Belize

Situated near the center of Lighthouse Reef some 43 miles from the Belize mainland, this spectacular blue hole is perhaps the most famous in the world. Commonly referred to as the Great Blue Hole, it was ranked No. 1 on a list of the 10 most amazing places on Earth by the Discovery Channel in 2012, and bears the stamp of approval from Jacques Cousteau after the famous oceanographer named it one of the world’s top 10 scuba sites in 1971. Belize’s blue hole is circular in shape, measures 984 feet (300 m) across and is 407 feet (124 m) deep. Thanks to these epic proportions, it can even be seen from space.

For recreational divers, this blue hole is best explored via liveaboard or a day charter from the mainland, which compensates for the long journey to get here and the short dive time at the hole itself with additional shallow, reef dives, as well as a visit to a nearby bird sanctuary. The blue-hole dive takes advanced divers to 132 feet (40 m), where they can see the submarine stalactites that make up the dive’s main attraction. At depth, there is limited light and life; in terms of flora and fauna, the highlight of this dive are the resident Caribbean reef sharks that can sometimes be seen on the descent and ascent. Dive times are short, and yet the unique nature of this dive means that it is still well worth doing at least once.

Egypt

Egypt’s blue hole is situated in the Red Sea, just a few miles north of Dahab and within easy reach of the shore. With a maximum depth of approximately 463 feet (130 m), this blue hole is quite different from its cousin in Belize. It’s connected via a tunnel known as The Arch to the open ocean, but as the top of the arch lies at 172 feet (52 meters), this section of the blue hole is only accessible to technical divers. Recreational divers hoping to experience something of the upper section of Dahab’s blue hole normally do so via a dive route known as Bells to Blue Hole, which offers the best of both worlds, combining wall and drift diving to dramatic effect.

The entrance for the Bells dive site is some 330 feet (100 m) north of the blue hole. Here, divers descend through a chimney in the reef to 86 feet (26 m), where a tunnel in the reef wall opens out into the ocean. Divers can then drift along the wall, searching for macro life on one side and keeping an eye out for passing pelagics on the other. Towards the end of the drift dive, divers ascend to 23 feet (7 m), where they can cross over a saddle in the reef into the blue hole itself. Here, divers spend the last part of their dive in the shallows, admiring the abundance of marine life supported by the sunlit inner walls of the structure, while also keeping an eye out for tec divers and free divers attempting to push new depth boundaries.

Bahamas

The Bahamas are home to several blue holes, including the deepest known saltwater blue hole in the world. West of Clarence Town on Long Island, Dean’s Blue Hole plunges to a depth of 663 feet (202 m), and can be accessed easily from shore, edged on one side as it is by a shallow lagoon and a beautiful, sandy beach. At the surface, this blue hole has a diameter of 82 to 115 feet (25 to 35 m), however, as divers descend down the entry shaft, the blue hole widens considerably at about 66 feet (20 m) into a cavern measuring at least 330 feet (100 m) across. Freediver William Trubridge made Dean’s Blue Hole famous when he used the hole’s incredible depths to break two separate freediving world records in 2010 and 2011, respectively.

Here, divers descend into the breathtaking chamber amidst the resident shoals of tarpon, lurking in the shadows at the edges of visibility. Shafts of sunlight filtering through the cavern’s opening lend the space a sense of eerie magic, and the blue abyss seems to stretch on forever past the recreational limit of 130 feet (40 m). The main attraction of this beautiful dive site is the novelty of finding oneself inside one of the planet’s most remarkable natural formations, but in the shallows, divers may encounter turtles, sharks and dolphins.

NOTE: By definition, blue-hole diving requires a certain level of experience and confidence, and can be dangerous if approached incorrectly. Divers will need excellent buoyancy to safely complete a blue-hole dive. Divers must constantly monitor their depth, time, and air consumption, be sure to book with a reputable charter or dive center.

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