The world is filled with strange and mysterious natural wonders but perhaps none hold as much mystery as the earth's blue holes, large marine caverns and water-filled sinkholes. Blue holes, which extend below sea level for most of their depth and may provide access to submerged cave passages, offer some of the world's most spectacular diving opportunities. These under-explored wonders were named for the contrast of the dark, deep blue color of their depths and the lighter color of the shallow water around them. In the Bahamas, which has the highest concentration of blue holes in the world, they have provided a great place for fossil discovery. Extinct animals, archaeological artifacts, and human remains have been found in blue holes.
Here, we take a look at the world's most fascinating blue holes in the Bahamas and beyond.
(MORE: 15 Incredible Swimming Holes Around the World)
1. Great Blue Hole, Belize
Located off the coast of Belize, the Great Blue Hole lies near the center of Lighthouse Reef and is part of the larger Belize Barrier Reef Reserve System, a UNESCO World Heritage site. The underwater sinkhole, which is over 400 feet deep, is a diver's dream—it's considered one of the top 10 diving sites in the world. Divers from all over the world travel here to dive in crystal-clear waters and see myriad species of marine life including, including Midnight Parrotfish and Caribbean reef shark, and spectacular coral formations.
2. Blue Hole, Dwerja, Gozo, Malta
Malta's Blue Hole, a circular formation of limestone rock, is located on the small island of Gozo in the Mediterranean Sea. One of the most popular diving sites in the Maltese Islands, the Blue Hole overlooks Azure Window, a limestone natural arch, and starts in a 32 foot-wide inland sea pool which leads into a large crevice and through to the open sea. Divers here can find several species of marine life such as octopus, starfish, fireworm, cardinal fish, barracuda, and bullet tuna, according to AFAR magazine.
3. Blue Hole, Dahab, Egypt
Located in east Sinai, near Dahab, Egypt on the coast of the Red Sea, the Blue Hole is a submarine sinkhole, around 300 ft deep. It has a shallow opening known as "the saddle," opening out to the sea, and a tunnel, known as "the arch." The site is dived almost every day by recreational divers. However, it has been called the "World's Most Dangerous Dive Site" due to several diving fatalities. Accidents happened as divers tried to find the tunnel through the reef connecting the Blue Hole and open water at about 170.6 feet depth.
4. Dean's Blue Hole, Long Island, Bahamas
5. Blue Holes of Palau
The Blue Holes of Palau, part of the Micronesia region in the western Pacific Ocean, features four vertical shafts that open on the top of the reef and descend to a large cavern that exits on the outer wall at about 82 feet, according to Lonely Planet.
6. Santa Rosa Blue Hole, New Mexico
An underwater cave connected to a deep lake in Santa Rosa, New Mexico, the Santa Rosa Blue Hole is known for its dangerous depths. Measurements in the 1970s suggest that the cavern is about 225 feet deep, but it's not known how far back it goes, or if it gets deeper, according to LiveScience. In 2013, team of divers and engineers from the Advanced Diver Magazine Exploration Foundation spent a week attempting to explore the Santa Rosa Blue Hole, where they discovered everything from Mayan relics to the skull of Antillothrix bernensis, an extinct species of New World monkey once found on the Dominican Republic.
7. Watling's Blue Hole, San Salvador, Bahamas
Watling's Blue Hole in San Salvador is one of the many blue holes of the Bahamian islands. Despite its location in the middle of a rainy tropical island, Watling’s Blue Hole has no fresh water indicating that the hole is connected to the ocean by an underground tunnel.
8. Blue Holes of Abaco, Bahamas
Abaco Island, the northernmost island in the Bahamas, is home to several blue holes, which have lured divers from all over the world. The inland blue holes generally reach depths of 80 feet to more than 330 feet, and may contain cave passages that extend off of the walls or floors, according to Advanced Diver Magazine. Some of the inland blue holes found in the island include Nancy's Blue Hole, located in a mangrove swamp; Far Side Blue Hole (also known as Magical Blue Hole), which has waters so clear that divers feel as though they are floating in air; and Sawmill Sink, a solution cave currently off limits to divers for research purposes.
9. and 10. Blue Holes of Andros, Bahamas
The Bahamas is home to many spectacular blue holes, but Andros Island is the "holy grail" location of blue holes for divers, according to many Bahamians. The island has the highest concentration of blue holes in the world, according to the Bahamas tourism board, with 178 blue holes on land (such as Guardian Blue Hole and Captain Bill's Blue Hole) and with at least 50 in the sea. They are home many unusual and unique cave fish and invertebrates, some not found anywhere else in the world.
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