Cave diving
October 28th, 2008
Despite these risks, water-filled caves attract cavers and speleologists due to their often unexplored nature, and present divers with a technical diving challenge. Caves often have a wide range of unique physical features, such as stalactites and stalagmites, and can contain unique flora and fauna not found elsewhere.
Cave diving is one of the most challenging and potentially dangerous kinds of diving and presents many diving hazards. Cave diving is a form of penetration diving, meaning that in an emergency a diver cannot ascend directly to the surface due to the cave's ceilings, and instead may have to swim horizontally. The underwater navigation through the cave system may be difficult and exit routes may be at considerable distance, requiring the diver to have sufficient breathing gas to make the journey, resulting in potential deep diving risks.
Visibility can be low, or non-existent. While a less-intensive kind of diving called cavern diving does not take divers beyond the outermost part of the cave reached by natural light, true cave diving can involve penetrations of many thousands of feet, well beyond the reach of sunlight. The level of darkness experienced creates an environment impossible to see in without an artificial form of light. Caves often contain sand, mud, clay, silt, or other sediment that can further reduce underwater visibility in seconds when stirred up.
Caves can carry strong water currents. Most caves emerge on the surface as either springs or siphons. Springs have out flowing currents, where water is coming up out of the Earth and flowing out across the land's surface. Siphons have inflowing currents where, for example, an above-ground river is going underground. Some caves are complex and have some tunnels with out flowing currents, and other tunnels with inflowing currents. If currents are not properly managed, they can cause serious problems for the diver.
Cave diving is perceived as one of the more dangerous sports in the world. This perception is arguable because the vast majority of divers who have lost their lives in caves have either not undergone specialized training or have had inadequate equipment for the environment. Many cave divers have suggested that cave diving is in fact statistically much safer than recreational diving due to the much larger barriers imposed by experience, training, and equipment cost.
There is no reliable worldwide database listing all cave diving fatalities. Such fractional statistics as are available, however, suggest that very few divers have ever died while following accepted protocols and while using equipment configurations recognized as acceptable by the cave diving community. In the very rare cases of exceptions to this rule there have always been unusual circumstances.
The cave diving community is a global one, partly due to the highly specialised nature with the resulting small numbers of practitioners at a local level.
However, cave diving practice can differ markedly by locality. One such difference is the use of a floating polypropylene guide line. Most cave divers in the U.S. balk at the use of any sort of floating guide line, 6 mm polypropylene line is the norm in UK because it does float - the line is regularly anchored to stones, lead weights, or whatever is needed and the floating keeps it clear of mud and silt. In Europe, thinner yet slightly buoyant line is typical. Cave diving practices in some localities may be different than those in other parts of the world because those caves require specialized techniques. It is always recommended that individuals contact someone familiar with a cave before venturing inside a cave.
Regularity in signs and warnings may also differ around the world. For example, warnings signs are rare in the UK.
Jacques-Yves Cousteau, co-inventor of the first SCUBA equipment, was both the world's first SCUBA diver and the world's first SCUBA cave diver. However, many cave divers penetrated caves prior to the advent of SCUBA with surface supplied UBA through the use of umbilical hoses and compressors. SCUBA diving in all its forms, including cave diving, has advanced in earnest since he introduced the aqua-Lung in 1943.
The Cave Diving Group (CDG) was established informally in the United Kingdom in 1935 to organise training and equipment for the exploration of flooded caves in the Mendip Hills of Somerset. The first dive was made by Jack Sheppard on 4 October 1936, using a home-made drysuit surface fed from a modified bicycle pump, which allowed Sheppard to pass Sump 1 of Swildon's Hole. Swildon's is an upstream feeder to the Wookey Hole resurgence system. The difficulty of access to the sump in Swildon's prompted operations to move to the resurgence, and the larger cave there allowed use of conventional "hard hat" equipment which was secured from the Siebe Gorman company. The left photograph on the standard diving dress page will give some indication of the scale of operations this entailed. In UK cave diving, the term "Sherpa" is used without a drop of irony for the people who carry the diver's gear, and before the development of SCUBA equipment such undertakings could be monumental operations.
Diving in the spacious third chamber of Wookey Hole led to a rapid series of advances, each of which was dignified by being given a successive number, until an air surface was reached at what is now known as "Chamber 9." Some of these dives were broadcast live on BBC radio, which must have been a quite surreal experience for both diver and audience.
The number of sites where standard diving dress could be used is clearly limited and there was little further progress before the outbreak of World War II reduced the caving community considerably. However, the rapid development of underwater warfare through the war made a lot of surplus equipment available. The CDG re-formed in 1946 and progress was rapid. Typical equipment at this time was a frogman rubber diving suit for insulation (water temperature in the UK is typically 4 °C), an oxygen diving cylinder, soda lime absorbent canister and counter-lung comprising a rebreather air system and an "AFLOLAUN," meaning "Apparatus For Laying Out Line And Underwater Navigation." The AFLOLAUN consisted of lights, line-reel, compass, notebook (for the survey), batteries, and more.
Progress was typically by "bottom walking", as this was considered less dangerous than swimming (note the absence of buoyancy controls). The use of oxygen put a depth limit on the dive, which was considerably mitigated by the extended dive duration. This was the normal diving equipment and methods until approximately 1960 when new techniques using wetsuits (which provide both insulation and buoyancy compensation), twin open-circuit SCUBA air systems, helmet-mounted lights and free-swimming with fins. The increasing capacity and pressure rating of air bottles also extended dive durations.
In the United States, Sheck Exley was a pioneering cave diver who first explored many Florida underwater cave systems, and many other underwater cave systems throughout the US and the world.
In the 1970s, cave diving greatly increased in popularity among divers in the United States. However, there were very few experienced cave divers and almost no formal classes to handle the surge in interest. The result was a large number of divers trying to cave dive without any formal training. This resulted in more than 100 fatalities over the course of the decade. The state of Florida came close to banning SCUBA diving around the cave entrances. The cave diving organizations responded to the problem by creating training programs and certifying instructors, in addition to other measures to try to prevent these fatalities. This included posting signs, adding no-lights rules, and other enforcements.
Since the 1980s, prevention measures to reduce diver fatalities have been successful, and today it is rare for an untrained diver to die in an underwater cave, despite later surges in popularity in the 1980s and 1990s. The 1980s saw a few refinements to the equipment used for cave diving, most importantly better lights and smaller batteries. In the 1990s equipment configurations became a little more standard than they had been in the past, due mostly to the WKPP's adaptation and popularization of the Hogarthian Rig, a concept credited to Bill "Hogarth" Main which states not to take what you don't need, keep it simple and streamline.
Documentary films made by Wes Skiles and Jill Heinerth have contributed to the increasing popularity of cave diving in the early 21st century.
Many sites today have strict rules about diving within one's level of training and requiring proof of that level, more so than most recreational diving sites elsewhere in the country. Today, the cave community is most focused on training, exploration, public awareness, and cave conservation. Different organizations place different emphasis on these priorities.
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 Cavern, Cave, Sinkhole, and Penetration.
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 7+-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 responsible for the administration of cave diving certification in Australia and mixed-gas and rebreather technologies are also now able to be used in many sites. All cave diving in the Mount Gambier area as well as 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.
Scuba Diving
July 18th, 2008
The term SCUBA arose during World War II and originally referred to United States combat frogmen's oxygen rebreathers, developed by Dr. Christian Lambertsen for underwater warfare. Today, scuba typically refers to the in-line open-circuit equipment, developed by Emile Gagnan and Jacques-Yves Cousteau, in which compressed gas (usually air) is inhaled from a tank and then exhaled into the water. However, rebreathers (both semi-closed circuit and closed circuit) are also self-contained systems (as opposed to surface-supplied systems) and are therefore classified as scuba.
Although the SCUBA is an acronym for "self-contained underwater breathing apparatus", usage is mainly as a normal word "scuba", it has become acceptable to refer to scuba as "scuba equipment" or "scuba apparatus" — an example of the linguistic RAS syndrome.
Water normally contains dissolved oxygen from which fish and other aquatic animals extract all their required oxygen as the water flows past their gills. Humans lack gills and do not otherwise have the capacity to breathe underwater unaided by external devices.
Early diving experimenters quickly discovered it is not enough simply to supply air in order to breathe comfortably underwater. As one descends, in addition to the normal atmospheric pressure, water exerts increasing pressure on the chest and lungs — approximately 1 bar or 14.7 psi for every 33 feet or 10 meters of depth — so the pressure of the inhaled breath must almost exactly counter the surrounding or ambient pressure in order to inflate the lungs.
By always providing the breathing gas at ambient pressure, modern demand valve regulators ensure the diver can inhale and exhale naturally and virtually effortlessly, regardless of depth.
Because the diver's nose and eyes are covered by a diving mask; the diver cannot breathe in through the nose, except when wearing a full face diving mask. However, inhaling from a regulator's mouthpiece becomes second nature very quickly.
Divers must avoid injuries caused by changes in air pressure. The weight of the water column above the diver causes an increase in air pressure in any compressible material (wetsuit, lungs, sinus) in proportion to depth, in the same way that atmospheric air causes a pressure of 14.7 pounds-force per square inch (101.3 kPa) at sea level. Pressure injuries are called barotrauma and can be quite painful, in severe cases causing a ruptured eardrum or damage to the sinuses. To avoid them, the diver equalizes the pressure in all air spaces with the surrounding water pressure when changing depth. The middle ear and sinus are equalized using one or more of several techniques, which is referred to as clearing the ears.
The mask is equalized by periodically exhaling through the nose.
If a drysuit is worn, it too must be equalized by inflation and deflation, similar to a buoyancy compensator.
