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Grand Bahama Island
The caves and caverns of Grand Bahama, contain an immense underwater cavern, with a vast, flooded, labyrinth of caverns, caves and submerged tunnels that honeycomb the entire island of Grand Bahama and the surrounding sea bed. The inland caves are not abundant with life, but do contain creatures living in the caves, other than the migrating gray snappers. Residents of these caves include a type of blind cave fish, and remipedia that don't pose any threat to cave divers.
The caves in the Bahamas were formed during the last ice age. With much of the Earth's water held in the form of glacial ice, the sea level fell hundreds of feet, leaving most of the Bahama banks, which are now covered in water, high and dry. Rain falling on the most porous limestone, slowly filtered down to sea level forming a lens where it contacted the denser salt water of the ocean permeating the spongy lime stone. The water at the interface, was acidic enough to dissolve away the limestone and form the caves. Then, as more ice formed and the sea level dropped even further, the caves became dry and rainwater dripping through the ceiling, over thousands of years, created the incredible crystal forests of stalagmites which now decorate the caves. Finally, when the ice melted and the sea level rose, the caves were reclaimed by the sea.
Central and Northern Florida, U.S.
The largest and most active cave diving community in the United States is in north-central Florida. The North Floridan Aquifer expels groundwater through numerous first-magnitude springs, each providing an entrance to the aquifer's labyrinthine cave system. These high-flow springs have resulted in Florida cave divers developing special techniques for exploring them, since some have such strong currents that it is impossible to swim against them.
The longest known underwater cave system in the USA, The Leon Sinks cave system, near Tallahassee, Florida, has multiple interconnected sinks and springs spanning two counties (Leon & Wakulla). One main resurgence of the system, Wakulla Springs, is explored exclusively by a very successful and pioneering project called the Woodville Karst Plain Project (WKPP), although other individuals and groups like the US Deep Cave Diving Team, have explored portions of Wakulla Springs in the past.
One of the deepest known underwater caves in the USA is Weeki Wachee Spring. Due to its strong outflow, divers have had limited success penetrating this first magnitude spring until 2007, when drought conditions eased the out-flowing water allowing team divers from Karst Underwater Research to penetrate to depths of 400 ft (120 m)
The Florida caves are formed from geologically young limestone with moderate porosity. The absence of speleothem decorations which can only form in air filled caves, indicates that the flooded Florida caves have a single genetic phase origin, having remained water filled even during past low sea levels. In plan form, the caves are relatively linear with a limited number of side passages allowing for most of the guidelines to be simple paths with few permanent tees. It is common practice for cave divers in Florida to joint a main line with a secondary line using a jump reel when exploring side passages, in order to maintain a continuous guideline to the surface.
Yucatan Peninsula, Mexico
While there is great potential for cave diving in the continental karst throughout Mexico, the vast majority of cave diving in Mexico occurs in the Yucatán Peninsula. While there are thousands of deep pit cenotes throughout the Yucatán Peninsula including in the states of Yucatán and Campeche, the extensive sub-horizontal flooded cave networks for which the peninsula is known are essentially limited to a 10 km wide strip of the Caribbean coastline in the state of Quintana Roo extending south from Cancun to the Tulum Municipality and the Sian Ka'an Biosphere Reserve, although some short segments of underwater cave have been explored on the north-west coast (Yucatán State).
In the Yucatán Peninsula, any surface opening where groundwater can be reached is called cenote, which is a Spanish form of the Maya word d’zonot. The cave systems formed as normal caves underwater, but upper sections drained becoming air filled during past low sea levels. During this vadose, or air filled state, abundant speleothem deposits formed. The caves and the vadose speleothem were subsequently reflooded and became hydraulically reactivated as rising sea levels also raised the water table. These caves are therefore polygenetic, having experienced more than one cycle of formation below the water table. Polygenetic coastal cave systems with underwater speleothem are globally common, with notable examples being on the Balearic Islands (Mallorca, Menorca) of Spain, the islands of the Bahamas, Bermuda, Cuba, and many more.
As with all cave speleothems, the underwater speleothems in the Yucatán Peninsula are fragile. If a diver accidentally breaks off a stalactite from the ceiling or other speleothem formation, it will not reform as long as the cave is underwater so active cave conservation diving techniques are paramount.
In plan form, the Quintana Roo caves are extremely complex with anastomotic interconnected passages. When cave diving through the caves, the pathways then appear to have many offshoots and junctions, requiring careful navigation with permanent tees or the implementation of jumps in the guideline.
The beginning of the 1980s brought the first cave divers from the U.S. to the Yucatán Peninsula, Quintana Roo to explore cenotes such as Carwash, Naharon and Maya Blue, but also to central Mexico where resurgence rivers such as Rio Mante, sinkholes such as Zacaton were documented.
In the Yucatán, the 1980s ended with the discoveries of the Dos Ojos and Nohoch Nah Chich cave systems which lead into a long ongoing competition of which exploration team had the longest underwater cave system in the world at the time, with both teams vying for first place.
The beginning of the 1990s led into the discovery of underwater caves such as Aereolito on the island of Cozumel, ultimately leading to the 5th biggest underwater cave in the world.
By the mid 1990s a push into the central Yucatán Peninsula by dedicated deep cave explorers discovered a large number of deep sinkholes, or pit cenotes, such as Sabak Ha, Utzil and deep caves such as Chacdzinikche, Dzibilchaltun, Karkirixche that have been explored and mapped. To this day these deep caves of the central Yucatán remain largely unexplored due to the sheer number of cenotes found in the State of Yucatán, as well as the depth involved that can be only tackled using technical diving techniques or rebreathers. In the end of the last millennium closed circuit rebreather (CCR) cave diving techniques were employed in order to explore these deep water filled caves.
By the end of the 1990s, "The Pit" in the Dos Ojos cave system located 5.8 km from the Caribbean coast had been discovered, and it is presently (2008) 119 m deep. At that time, technical diving and rebreather equipment and techniques became common place.
By the turn of the millennium the longest underwater cave system at that time, Ox Bel Ha was established by cave diving explorers whose combined efforts and information helped join segments of previously explored caves. The use of hand held GPS technology and aerial and satellite images for reconnaissance during exploration became common. New technology such as rebreathers and diver propulsion vehicles (DPVs) became available and were utilized for longer penetration dives. As of October 2010, Ox Bel Ha includes 182 km of underwater passage (See QRSS for current statistics).
Active exploration continues in the new millennium. Most cave diving exploration is now conducted on the basis of "mini projects" lasting 1 – 7 days, and occurring many times a year, and these may include daily commutes from home to jungle dive base camps located within 1 hour from road access.
Starting in 2006 a number of large previously explored and mapped cave systems have been connected utilizing sidemount cave diving techniques and many times no-mount cave diving techniques in order to pass through these tight cave passages, creating the largest connected underwater cave system on the planet, Sac Actun, which presently has a length extent of 215 km (See QRSS for current statistics).
Many cave maps have been published by the Quintana Roo Speleological Survey (QRSS).
UK requirements are generally that all people wishing to take up cave diving must be competent cavers before they start cave diving. This is primarily because most British cave dives are at the far end of dry caves. There are individuals that begin cave diving directly from the recreational diving, but they represent a minority in the UK, and represent only a few percent of the Cave Diving Group (CDG).
Australian cave diving and the CDAA
Australia has many spectacular water filled caves and sinkholes, but unlike the UK, most Australian cave divers come from a general ocean-diving background. The "air-clear" water of the sinkholes and caves can be found in the Mount Gambier area of south-eastern Australia. The first cave and sinkhole dives here took place in the very late 1950s, and until the mid 1980s divers generally used single diving cylinders and homemade torches, and reels, resulting in most of their explorations being limited.
A series of tragedies between 1969 and 1973 in which 11 divers drowned (including a triple and a quadruple fatality) in just four karst features - "Kilsbys Hole", "Piccaninnie Ponds", "Death Cave" and "The Shaft" - created much public comment and led to the formation of the Cave Divers Association of Australia (CDAA) Inc. in September 1973. As a consequence of the CDAA's assessment programs, divers are rated at various levels, and today they comprise Deep Cavern, Cave, and Advanced Cave.
During the 1980s the Nullarbor Plain was recognized as a major cave-diving area, with one cave, Cocklebiddy, being explored for more than 6 kilometers, involving the use of large sleds to which were attached numerous diving cylinders and other paraphernalia, and which were then laboriously pushed through the cave by the divers. In more recent years divers have been utilizing compact diver-towing powered scooters, but the dive is still technically extremely challenging. A number of other very significant caves have also been discovered during the past 10 years or so; the 10+ (Lineal) kilometre long Tank Cave near Mount Gambier, other very large features on the Nullarbor and adjacent Roe Plain as well as a number of specific sites elsewhere, and nowadays the cave diving community utilizes many techniques, equipment and standards from the U.S. and elsewhere.
The CDAA is one of a number of organisations responsible for the administration of cave diving certification in Australia. Mixed-gas and rebreather technologies can now be used in many sites. All cave diving in the Mount Gambier area as well as at some New South Wales sites and the Nullarbor requires divers to be members of the CDAA, whether in the capacity of a visitor or a trained and assessed member.
In Brazil there is cavern diving in Chapada da Diamantina, in Bahia state; Bonito, in Mato Grosso do Sul state; and Mariana, where there is also cave diving (visiting Mina da Passagem), in Minas Gerais state.
To dive in public parks, for example those in Bonito, one must be adequately certified by an agency recognized by IBAMA - Instituto Brasileiro de Administração do Meio Ambiente, a federal organ. For cave diving in Mariana a cave diver certification will be required.
In the north west of Sardinia, close to Porto Conte bay, Alghero territory, there is the most important cave diving site in the Mediterranean Sea. Thanks to the huge limestone cliffs of Capo Caccia and Punta Giglio there are more than 300 caves above and below water, with about 30 large, and many smaller, underwater sea caves. The Nereo Cave is the most important and it is considered also the largest in the Mediterranean Sea. On the east side of Sardinia there are many underwater cave systems starting from the Gennargentu Mountains, with underwater rivers which arrive at the sea by different, lengthy routes. Here one of the deepest fresh water caves exits at more than 110 m (360 ft) depth.
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