Hole Details A seemingly random hole in the middle of nowhere, the Black Hole of Andros gets its name because of the toxic algae which inhabits its surface causing it to have a black color as opposed to the normal blue of other "blue holes". As a result of this toxic algae, it is a natural hazard and needs to be avoided at all costs.

This toxic sinkhole is 1,000 feet (333 meters) across and 154 feet (47 meters) deep. While not extremely deep, the high level of sulfur can cause death if someone tries to swim in it. This is because also in addition to the sulfur, the bacteria and microorganisms can reduce levels of oxygen and increase levels of poisonous hydrogen sulfide in the water. 50 feet down into this black hole, there is zero oxygen, and very high levels of hydrogen sulfide.

This danger is further exasperated by the fact that it is surrounded by several meters of mud which makes it inaccessible except by helicopter. Below the surface the temperature is very high, which is unexplainable except perhaps by the presence of the bacteria which could be causing it to heat up.

Past 50 feet it becomes very hot which causes divers' skin to hurt like it would if you ran your hand under hot water, and combined with the hydrogen sulfide which causes all cuts, even the most minor to experience a burning sensation. Hydrogen sulfide is also a neurotoxin that can cause divers to black out, and subsequently drown.

Unlike blue holes which are thought to form from the bottom up, black holes are thought to form from the top down. It is theorized that over centuries the surface is eroded, causing the hole to become very deep. Scientists believe that this black hole was formed when a cave roof collapsed, causing a near perfect circle.

The surface of the water has a ph of 8.6, but this drops to 6.5 below the 3 foot thick layer of bacteria that lines the surface, resulting in acidic water that increases the danger of this mysterious black hole. This is the largest hole in the Bahamas, and it is so large that it can even be seen from space.

Hole Details Unlike the terrifying depths of the Black Hole of Andros, the Bimmah hole in Oman is a popular swim spot for tourists and divers. Bimmah hole is about 120 feet wide and 60 feet deep, and is mostly covered by a limestone cavern. It was most likely formed over a couple thousand years of erosion, and partly possibly due to a cavern collapse. Bimmah has crystal blue water and contains little friendly fish that have been known to happily nibble harmlessly at people's toes.

Bimmah is located about 1600 feet from the ocean, and is situated between the Gulf of Oman and Highway 17. It is about 70 miles (113 kilometers) southeast of Muscat in Dabab Village. There is a staircase built in so that tourists can safely descend into the primary opening of the Bimmah sinkhole and connected caverns.

Hole Details Mount Baldy's is not your typical hole, but rather a series of randomly appearing holes that swallow people alive. It seems like a normal beach, but out of nowhere holes open open and swallow whatever is above, only to shortly seal back in with sand. In The cause of these holes are unknown, and as a result of the danger, signs are posted warning tourists.

Mount Baldy sand dunes are located in the Indiana Dunes National Lakeshore, a national park in Indiana on the south side of Lake Michigan, between Gary and Michigan City. The park is 15 miles long. In 2014 a family had visited the beach, and their 6-year-old boy got swallowed alive by the dunes. The family could not find the boy, but 3 and a half hours later with a search and rescue team of 50 people, they found the boy lifeless and unconscious 12 feet below the surface, with no breath and no pulse.

This did not end in tragedy, fortunately; the boy was revived and his life was taken back from the dangerous and deadly dunes. What causes these random sinkholes? Could there be a sand creature beneath the surface, hungry for human flesh? Unlikely, but the cause of these randomly appearing holes on Mount Baldy still baffles scientists today.

Hole Details The Sawmill Sink is not originally a natural hole, but a manmade one; still, its allure cannot go unnoticed. The hole began as an archaeological dig, but soon it filled with water and preserved several-hundred-year-old fossils of giant tortoises, birds, flowers, seeds, and even the remains of a giant crocodile.

While not a naturally occurring blue hole, it effectively functions as a blue hole preserving fossils from a few hundred years ago that would likely have gone otherwise unnoticed. Some evolutionists even tried to use this hole as a scandal trying to claim that "pre-human" fossils have been found, although in reality the fossils are just a few hundred years old at the oldest. Some species whose fossils were found are now extinct, including a certain species of giant tortoise and giant crocodiles which were likely killed off by human inhabitants.

The Sawmill Sink is 102 feet (34 meters) deep at the deepest, and 150 feet wide at the widest. It is linked to a cave system which is 162 feet (54 meters) deep and 1800 feet (600 meters) long. It gets its name from a 1900's sawmill operation that resulted in its creation.

The water is a clear blue, similar to other blue holes in the Abaco region of the Bahamas. 81 feet (27 meters) down, the water transitions into an opaque, dark water that cannot be seen through, containing bacteria and microorganisms which produce hydrogen sulfide. Below that, anoxic marine water which is influenced by tidal forces flows freely underneath throughout the system.

Hole Details A natural sinkhole, Red Lake in Croatia is 1,739 feet (530 meters) deep and has a volume of about 900 million to 1 billion cubic feet (25–30 million cubic meters) making it the largest known sinkhole in the world.

Experts believe that Red Lake was formed when a cave underneath collapsed. It is home to the delminichthys adspersus species of fish, which looks similar to a trout, providing food for the giant lake monsters who dwell at the bottom. Just kidding, no lake monsters.

Hole Details Discovered in June of 2016, this blue hole is the most recent giant hole discovery. Dragon's Hole is in fact now the largest known blue hole in the world, surpassing the second largest by a huge 300 feet deeper than Dean's Hole in the Bahamas. Dragon's Hole is 987 feet deep.

Dragon's Hole is located in the Paracel Islands in China, also called Xisha in Chinese. Actually, China, Taiwan and Vietnam all claim these islands as part of their territory.

While only recently has the depth of almost 1,000 feet been known, in fact Dragon's Hole has been known by locals for centuries. It is said that a 16th-century Chinese novel “Journey to the West” referenced this blue hole.

Hole Details Glory Hole is not a natural hole, but it is a fantastic one. Located at the top of Monticello Dam in Napa California, this hole is a human-designed spillway which is opened up when the water level gets too high. It drains at the bottom of the dam.

Glory Hole is 78 feet at the largest, and 28 feet wide at the bottom. It is the largest spillway in the world, and the spillway and dam were built between 1953 and 1957. During the dry season, skateboarders sometimes use the side of it as a ramp. If they fell in they would probably not survive.



In fact there used to be a town underneath the water. When the dam was created it flooded the town. Sometimes when the water level gets low enough some of the town can be seen emerging from the manmade lake.

It might look fun to jump in this hole and get shot out at the bottom, but actually I doubt you would survive the plunge. This spillway hole spills at a rate of 48,800 cubic feet per second, and travels down 700 feet before being shot out of an enormous concrete hole in the side of the dam at the bottom.

Hole Details Dean's Blue Hole is not the largest, coming in at second place to Dragon's Hole; but it is much more famous and well known. There is a cool documentary on it showing how deep it goes, and describing the mystery behind how it came into existence.

In the documentary it is shown that there is a suction effect, and further down there are channels flowing out of it. Divers have tried to go it, but the farther they go into the channel tunnels the greater the suction effect. Eventually they have to turn around and use their arms to pull themselves back because the section force is too strong.



Dean's Blue Hole holds a lot of unexplained mysteries. What is at the end of the channels? How deep does it really go? What is causing the suction? How did it form? How long has it been there?

Maybe if you went into the channel tunnels you would be sucked into the center of the Earth. Who knows, but it leaves a lot up to the imagination, especially if you have ever read Jules Verne's books "Journey to the Center of the Earth" or "20,000 Leagues Under the Sea".

Hole Details Aptly named, the Door To Hell in Turkmenistan looks just like it is described. Who knows how this hole originally began, but how it turned into a hole of fire has a good story behind it. It isn't molten lava, but actually burning natural gas.

The story goes that in 1971 a Soviet drilling rig came to a cavern filled with natural gas. For safety, the geologists decided to burn it out, so they lit a match and dropped it in. Ok just kidding I don't know how they lit it but they did decide to burn it up, or so the story goes.



They thought that it would burn out in a couple of days, but 40 years later, it is still burning today. Sometimes locals will throw in matches and you will see brilliant bursts of flames. It's a great place to burn the witches, no stake needed! Just toss them straight into hell.

The total hole size is 57,587 square feet (5,350 square meters), the size of an American football field. It is surrounded by camping grounds for people who want to have a surreal camping experience right next to the Door to Hell.

Hole Details The Great Blue Hole in Belize takes the number one spot because it is a popular tourist and scuba diving destination. With its near perfect circle, crystal-clear blue waters, and many amazing yet docile forms of sea life including beautiful corals and brilliant tropical fish, the Great Blue Hole is a sight to see and visit.

The total size of the Great Blue Hole is 984 feet (300 meters) wide, and 410 feet (125 meters) deep. It may not be the deepest blue hole in the world but it is the world's largest natural formation. Located in the Barrier Reef Reserve System, it is protected by the United Nations Educational, Scientific and Cultural Organization (UNESCO).

It was likely formed about 3 or 4 thousand years ago, and there are stalactites and stalagmites which are somewhere between decades and centuries old. How it formed is unknown, but it was probably formed when a cavern below collapsed, like happened with many other holes.



There are also tiger sharks but divers take videos of them so they are pretty harmless. Of course, at its depth and being the ocean, anything could be down there so I wouldn't recommend to go alone. At least one great white shark has been filmed. Make sure that you don't have any cuts if you go diving! Even a papercut can create a shark frenzy. There are definitely sharks there, but they would probably take the easier bait of the smaller fish, there is no reason to attack humans.

It is definitely worth a visit to the Great Blue Hole in Belize. It is undeniably beautiful and it will certainly be the experience of a lifetime.