The Great Blue Hole is a giant marine sinkhole off the coast of Belize. It lies near the center of Lighthouse Reef, a small atoll 70 km (43 mi) from the mainland and Belize City. The hole is circular in shape, 318 m (1,043 ft) across and 124 m (407 ft) deep. It was formed during several episodes of quaternary glaciation when sea levels were much lower. Analysis of stalactites found in the Great Blue Hole shows that formation took place 153,000; 66,000; 60,000; and 15,000 years ago. As the ocean began to rise again, the cave was flooded. The Great Blue Hole is a part of the larger Belize Barrier Reef Reserve System, a World Heritage Site of the United Nations Educational, Scientific and Cultural Organization (UNESCO).
A blue hole is a large marine cavern or sinkhole, which is open to the surface and has developed in a bank or island composed of a carbonate bedrock. Blue holes typically contain tidally influenced water of fresh, marine, or mixed chemistry. They extend below sea level for most of their depth and may provide access to submerged cave passages. Well-known examples can be found in South China Sea, Belize, the Bahamas, Guam, Australia, and Egypt.
Belize is an independent and sovereign country located on the north eastern coast of Central America. Belize is bordered on the northwest by Mexico, on the east by the Caribbean Sea, and on the south and west by Guatemala. It has an area of 22,970 square kilometres (8,867 sq mi) and a population of 387,879 (2017). Its mainland is about 180 mi (290 km) long and 68 mi (110 km) wide. It has the lowest population and population density in Central America. The country's population growth rate of 1.87% per year (2015) is the second highest in the region and one of the highest in the Western Hemisphere.
Lighthouse Reef is an atoll in the Caribbean Sea, the easternmost part of the Belize Barrier Reef and one of its three atolls, the other two being Turneffe Atoll and Glover's Reef. Lighthouse Reef is located about 80 kilometres (50 mi) southeast of Belize City. The atoll is of oblong shape, approximately 35 kilometres (22 mi) long from north to south, and about 8 kilometres (5.0 mi) wide. It forms a shallow sandy lagoon with an area of 120 square kilometres (46 sq mi) and a depth between 2 to 6 metres deep.
This site was made famous by Jacques Cousteau, who declared it one of the top five scuba diving sites in the world. In 1971 he brought his ship, the Calypso , to the hole to chart its depths. 21 m (69 ft), 49 m (161 ft), and 91 m (299 ft). Stalactites were retrieved from submerged caves, confirming their previous formation above sea level. Some of these stalactites were also off-vertical by 5˚ in a consistent orientation, indicating that there had also been some past geological shift and tilting of the underlying plateau, followed by a long period in the current plane. The tilt indicates that this was a movement of the land, rather than a rise in sea level alone.Investigations by this expedition confirmed the hole's origin as typical karst limestone formations, formed before rises in sea level in at least four stages, leaving ledges at depths of
Jacques-Yves Cousteau was a French naval officer, explorer, conservationist, filmmaker, innovator, scientist, photographer, author and researcher who studied the sea and all forms of life in water. He co-developed the Aqua-lung, pioneered marine conservation and was a member of the Académie française.
Scuba diving is a mode of underwater diving where the diver uses a self-contained underwater breathing apparatus (scuba), which is completely independent of surface supply, to breathe underwater. Scuba divers carry their own source of breathing gas, usually compressed air, allowing them greater independence and freedom of movement than surface-supplied divers, and longer underwater endurance than breath-hold divers. Although the use of compressed air is common, a new mixture called enriched air (Nitrox) has been gaining popularity due to its benefit of reduced nitrogen intake during repetitive dives. Open circuit scuba systems discharge the breathing gas into the environment as it is exhaled, and consist of one or more diving cylinders containing breathing gas at high pressure which is supplied to the diver through a regulator. They may include additional cylinders for range extension, decompression gas or emergency breathing gas. Closed-circuit or semi-closed circuit rebreather scuba systems allow recycling of exhaled gases. The volume of gas used is reduced compared to that of open circuit, so a smaller cylinder or cylinders may be used for an equivalent dive duration. Rebreathers extend the time spent underwater compared to open circuit for the same gas consumption; they produce fewer bubbles and less noise than open circuit scuba which makes them attractive to covert military divers to avoid detection, scientific divers to avoid disturbing marine animals, and media divers to avoid bubble interference.
RV Calypso is a former British Royal Navy minesweeper converted into a research vessel for the oceanographic researcher Jacques-Yves Cousteau, equipped with a mobile laboratory for underwater field research. It was severely damaged in 1996, and was planned to undergo a complete refurbishment in 2009-2011. The ship is named after the Greek mythological figure Calypso.
Initial measured depth of Great Blue Hole was 125 m (410 ft) which is the most often cited depth up to this day. An expedition by the Cambrian Foundation in 1997 measured the hole's depth as 124 m (407 ft) at its deepest point. This difference in measurement can be explained by ongoing sedimentation or by imprecision in measurements. The expedition's goal was to collect core samples from the Blue Hole's floor and document the cave system. To accomplish these tasks, all of the divers had to be certified in cave diving and mixed gases.
A core sample is a cylindrical section of (usually) a naturally occurring substance. Most core samples are obtained by drilling with special drills into the substance, for example sediment or rock, with a hollow steel tube called a core drill. The hole made for the core sample is called the "core bowling". A variety of core samplers exist to sample different media under different conditions. More continue to be invented on a regular basis. In the coring process, the sample is pushed more or less intact into the tube. Removed from the tube in the laboratory, it is inspected and analyzed by different techniques and equipment depending on the type of data desired.
A cave or cavern is a natural void in the ground, specifically a space large enough for a human to enter. Caves often form by the weathering of rock and often extend deep underground. The word cave can also refer to much smaller openings such as sea caves, rock shelters, and grottos, though strictly speaking a cave is exogene, meaning it is deeper than its opening is wide, and a rock shelter is endogene.
Cave diving is underwater diving in water-filled caves. It may be done as an extreme sport, a way of exploring flooded caves for scientific investigation, or for the search for and recovery of divers lost while diving for one of these reasons. The equipment used varies depending on the circumstances, and ranges from breath hold to surface supplied, but almost all cave diving is done using scuba equipment, often in specialised configurations with redundancies such as sidemount or backmounted twinset. Recreational cave diving is generally considered to be a type of technical diving due to the lack of a free surface during large parts of the dive, and often involves decompression.
In December 2018, two submarines descended into the Blue Hole, in an attempt to map its interior. Using sonar scanning, the team was nearly able to complete a 3-D map of the 1,000 foot wide hole.
Sonar is a technique that uses sound propagation to navigate, communicate with or detect objects on or under the surface of the water, such as other vessels. Two types of technology share the name "sonar": passive sonar is essentially listening for the sound made by vessels; active sonar is emitting pulses of sounds and listening for echoes. Sonar may be used as a means of acoustic location and of measurement of the echo characteristics of "targets" in the water. Acoustic location in air was used before the introduction of radar. Sonar may also be used in air for robot navigation, and SODAR is used for atmospheric investigations. The term sonar is also used for the equipment used to generate and receive the sound. The acoustic frequencies used in sonar systems vary from very low (infrasonic) to extremely high (ultrasonic). The study of underwater sound is known as underwater acoustics or hydroacoustics.
This is a popular spot among recreational scuba divers who are lured by the opportunity to dive in sometimes crystal-clear water and meet several species of fish, including Midnight Parrotfish, Caribbean reef shark, and other juvenile fish species. Other species of sharks, such as the bull shark and hammerheads, have been reported there, but are not regularly sighted. Usually, day trips to the Great Blue Hole are full-day trips from the coastal tourist communities in Belize.
The Caribbean reef shark is a species of requiem shark, belonging to the family Carcharhinidae. It is found in the tropical waters of the western Atlantic Ocean from Florida to Brazil, and is the most commonly encountered reef shark in the Caribbean Sea. With a robust, streamlined body typical of the requiem sharks, this species is difficult to tell apart from other large members of its family such as the dusky shark and the silky shark. Distinguishing characteristics include dusky-colored fins without prominent markings, a short free rear tip on the second dorsal fin, and tooth shape and number.
The bull shark, also known as the Zambezi shark in Africa, and Lake Nicaragua shark in Nicaragua, is a requiem shark commonly found worldwide in warm, shallow waters along coasts and in rivers. The bull shark is known for its aggressive nature, and presence in warm, shallow brackish and freshwater systems including estuaries and rivers.
The hammerhead sharks are a group of sharks in the family Sphyrnidae, so named for the unusual and distinctive structure of their heads, which are flattened and laterally extended into a "hammer" shape called a cephalofoil. Most hammerhead species are placed in the genus Sphyrna, while the winghead shark is placed in its own genus, Eusphyra. Many, but not necessarily mutually exclusive, functions have been postulated for the cephalofoil, including sensory reception, manoeuvering, and prey manipulation. Hammerheads are found worldwide in warmer waters along coastlines and continental shelves. Unlike most sharks, hammerheads usually swim in schools during the day, becoming solitary hunters at night. Some of these schools can be found near Malpelo Island in Colombia, the Galapagos Islands in Ecuador, Cocos Island off Costa Rica, and near Molokai in Hawaii. Large schools are also seen in the waters off southern and eastern Africa.
On-shore caves of similar formation, as large collapsed sinkholes, are well known in Belize and in the Yucatán Peninsula, where they are known as cenotes . Unlike the mainland cenotes which often link to underwater cave systems, there is little evidence of horizontal development in the Blue Hole.
The Yucatán Peninsula, in southeastern Mexico, separates the Caribbean Sea from the Gulf of Mexico, with the northern coastline on the Yucatán Channel. The peninsula lies east of the Isthmus of Tehuantepec, a northwestern geographic partition separating the region of Central America from the rest of North America. It is approximately 181,000 km2 (70,000 sq mi) in area, and is almost entirely composed of limestone.
A cenote is a natural pit, or sinkhole, resulting from the collapse of limestone bedrock that exposes groundwater underneath. Especially associated with the Yucatán Peninsula of Mexico, cenotes were sometimes used by the ancient Maya for sacrificial offerings.
In 2012 Discovery Channel ranked the Great Blue Hole as number one on its list of "The 10 Most Amazing Places on Earth".In 2018, They featured a two-hour special titled Discovery Live: Into the Blue Hole featuring Fabien Cousteau and Richard Branson.
Even though the Great Blue Hole is considered a bucket-list dive, one should be aware that it is not for divers of all skill levels – a prerequisite is logging more than 24 dives. It is also not a 'colourful dive', instead, divers witness a dark cave with impressive stalactites.
A sinkhole, also known as a cenote, sink, sink-hole, swallet, swallow hole, or doline, is a depression or hole in the ground caused by some form of collapse of the surface layer. Most are caused by karst processes – for example, the chemical dissolution of carbonate rocks or suffosion processes. Sinkholes vary in size from 1 to 600 m both in diameter and depth, and vary in form from soil-lined bowls to bedrock-edged chasms. Sinkholes may form gradually or suddenly, and are found worldwide.
Deep diving is underwater diving to a depth beyond the norm accepted by the associated community. In some cases this is a prescribed limit established by an authority, and in others it is associated with a level of certification or training, and it may vary depending on whether the diving is recreational, technical or commercial. Nitrogen narcosis becomes a hazard below 30 metres (98 ft) and hypoxic breathing gas is required below 60 metres (200 ft) to lessen the risk of oxygen toxicity. Professional divers may use an atmospheric diving suit that allows very deep dives of up to 610 metres (2,000 ft).
Sheck Exley was an American cave diver. He is widely regarded as one of the pioneers of cave diving, and he wrote two major books on the subject: Basic Cave Diving: A Blueprint for Survival and Caverns Measureless to Man. On February 6, 1974, Exley became the first chairman of the Cave Diving Section of the National Speleological Society. During his career, he established many of the basic safety procedures used in cave and overhead diving today. Exley was also a pioneer of extreme deep scuba diving.
The Blue Hole is a diving location on the southeast Sinai, a few kilometres north of Dahab, Egypt on the coast of the Red Sea.
The Cave Diving Group (CDG) is a United Kingdom-based diver training organisation specialising in cave diving.
Dos Ojos is part of a flooded cave system located north of Tulum, on the Caribbean coast of the Yucatán Peninsula, in the state of Quintana Roo, Mexico. The exploration of Dos Ojos began in 1987 and still continues. The surveyed extent of the cave system is 82 kilometers (51 mi) and there are 28 known sinkhole entrances, which are locally called cenotes. In January 2018, a connection was found between Sistema Dos Ojos and Sistema Sac Actun. The smaller Dos Ojos became a part of Sac Actun, making the Sistema Sac Actun the longest known underwater cave system in the world.
The Belize Barrier Reef is a series of coral reefs straddling the coast of Belize, roughly 300 meters (980 ft) offshore in the north and 40 kilometers (25 mi) in the south within the country limits. The Belize Barrier Reef is a 300-kilometer (190 mi) long section of the 900-kilometer (560 mi) Mesoamerican Barrier Reef System, which is continuous from Cancún on the north-eastern tip of the Yucatán Peninsula through the Riviera Maya and up to Honduras, making it as of 2019 the World's largest coral reef system in the world. It is Belize's top tourist destination, popular for scuba diving and snorkeling and attracting almost half of its 260,000 visitors. It is also vital to the country's fishing industry.
The Devil's Throat is an underwater cave formation near the island of Cozumel, Mexico, at Punta Sur in the Arrecifes de Cozumel National Park; it starts at approximately 80 feet (24 m) of depth and opens up at approximately 135 ft (41 m) - right at the edge of recreational dive limits.
Palancar Reef is a large coral reef on the southwest side of the island of Cozumel and is part of the Arrecifes de Cozumel National Park. The site, popular with scuba divers, is divided into several sections based on depth and coral formations. Dive depths range from 50 to 110 feet, with coral swim-throughs in many places.
Nuno Gomes is a scuba diver who lives in New York City. Born in Lisbon, his family relocated to Pretoria when he was 14 years old. He is the holder of two world records in deep diving, the cave diving record from 1996 to the present and the sea water record from 2005 to 2014.
The Maldives has become one of the world's best scuba diving destinations because of the white sand beaches, coral reefs, clear warm waters, numerous scuba diving sites and rich marine life.
The Cave Divers Association of Australia (CDAA) is a cave diving organisation which was formed in September 1973 to represent the interests of recreational scuba divers who dive in water‐filled caves and sinkholes principally in the Lower South East of South Australia (SA) and secondly in other parts of Australia. Its formation occurred after a series of diving fatalities in waterfilled caves and sinkholes in the Mount Gambier region between 1969 and 1973 and in parallel to a South Australian Government inquiry into these deaths. The CDAA’s major achievement has been the dramatic reduction of fatalities via the introduction of a site rating scheme and an associated testing system which was brought in during the mid-1970s. While its major area of operation is in the Limestone Coast region of SA, it administers and supports cave diving activity in other parts of Australia including the Nullarbor Plain and Wellington, New South Wales.
Jonathan Bird's Blue World is a family-friendly underwater science/adventure television program. The program is hosted by underwater cinematographer Jonathan Bird. This series airs on public television stations in the US. The program is designed for family viewing, and each segment finds Bird trying to unravel a mystery, witness an animal behavior or explore an underwater environment. The first season consisted of 5 half-hour programs filmed in standard definition, and the subsequent seasons were all shot in high-definition. The second and third seasons each won four New England Emmy Awards. The fourth season was nominated for a 2013 National Daytime Emmy Award. The pilot episode from season 1 won a CINE Golden Eagle Award. The program is magazine format with each television episode consisting of 2-3 segments. These segments appear individually on YouTube and the Blue World website as webisodes. There are currently 6 seasons.
Richelieu Rock is a dive site in Thailand in the Andaman Sea about 200 km northwest of Phuket. It is part of the Mu Koh Surin marine park although being about 18 km east of Surin Island.
Little Blue Lake is a water-filled doline in the Australian state of South Australia located in the state's south-east in the locality of Mount Schank about 20 kilometres (12 mi) south of the municipal seat of Mount Gambier. It is notable locally as a swimming hole and nationally as a cave diving site. It is managed by the District Council of Grant and has been developed as a recreational and tourism venue.
The following outline is provided as an overview of and topical guide to underwater diving: