History

Main article: timeline of underwater technology

Original Aqualung SCUBA set

The first commercially successful scuba sets were the Aqualung open-circuit units 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, and the descendants of these systems are still the most popular units today.

The open circuit systems were developed after Cousteau had a number of incidents of oxygen toxicity using a rebreather system, in which exhaled air is reprocessed to remove carbon dioxide. Modern versions of rebreather systems (both semi-closed circuit and closed circuit) are still available today, and form the second main type of scuba unit, most commonly used for technical diving, such as deep diving.

Etymology

The term SCUBA (an acronym for Self-Contained Underwater Breathing Apparatus) arose during World War II, and originally referred to United States combat frogmen’s oxygen rebreathers, developed by Dr. Christian Lambertsen for underwater warfare.

The word SCUBA began as an acronym, but it is now usually thought of as a regular wordcuba. It has become acceptable to refer to “scuba equipment” or “scuba apparatus”xamples of the linguistic RAS syndrome.

Types of diving

Professional diver performing underwater welding

See also: Recreational diving and Professional diving

Scuba diving may be performed for a number of reasons, both personal and professional. Most people begin though recreational diving, which is performed purely for enjoyment and has a number of distinct technical disciplines to increase interest underwater, such as cave diving, wreck diving, ice diving and deep diving.

Divers may be employed professionally to perform tasks underwater. Most of these commercial divers are employed to perform tasks related to the running of a business involving deep water, including civil engineering tasks such as in oil exploration, underwater welding or offshore construction. Commercial divers may also be employed to perform tasks specifically related to marine activities, such as naval diving, including the repair and inspection of boats and ships, salvage of wrecks or underwater fishing, like spear fishing.

Other specialist areas of diving include military diving, with a long history of military frogmen in various roles. They can perform roles including direct combat, infiltration behind enemy lines, placing mines or using a manned torpedo, bomb disposal or engineering operations. In civilian operations, many police forces operate police diving teams to perform search and recovery or search and rescue operations and to assist with the detection of crime which may involve bodies of water. In some cases diver rescue teams may also be part of a fire department or lifeguard unit.

Lastly, there are professional divers involved with the water itself, such as underwater photography or underwater filming divers, who set out to document the underwater world, or scientific diving, including marine biology and underwater archaeology.

Reasons for diving may include:

Type of diving

Classification

aquarium maintenance in large public aquariums

commercial, scientific

boat and ship inspection, cleaning and maintenance

commercial, naval

cave diving

technical, recreational

civil engineering in harbors, water supply, and drainage systems

commercial

crude oil industry and other offshore construction and maintenance

commercial

demolition and salvage of ship wrecks

commercial, naval

diver training for reward

professional

fish farm maintenance

commercial

fishing, e.g. for abalones, crabs, lobsters, pearls, scallops, sea crayfish, sponges

commercial

frogman, manned torpedo

military

harbor clearance and maintenance

commercial, military

media diving: making television programs, etc.

professional

mine clearance and bomb disposal, disposing of unexploded ordnance

military, naval

pleasure, leisure, sport

recreational

underwater photography

professional, recreational

policing: diving to investigate or arrest unauthorized divers

police diving, military, naval

search and recovery diving

commercial

search and rescue diving

police

spear fishing

professional (occasionally), recreational

stealthy infiltration

military

marine biology

scientific, recreational

underwater tourism

recreational

underwater archaeology (shipwrecks; harbors, and buildings)

scientific, recreational

underwater welding

commercial

Breathing underwater

For more information, see Diving regulator.

Scuba diver on reef

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. Although the feasibility of filling and artificially ventilating the lungs with a dedicated liquid (Liquid breathing) has been established for some time, the size and complexity of the equipment allows only for medical applications with current technology.

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 lungspproximately 1 bar or 14.7 psi for every 33 feet or 10 meters of deptho the pressure of the inhaled breath must almost exactly counter the surrounding or ambient pressure to inflate the lungs. It generally becomes difficult to breathe through a tube past three feet under the water.

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.

Open-circuit

The most commonly used scuba set today is the “single-hose” open circuit 2-stage diving regulator, coupled to a single pressurized gas cylinder, with the first stage on the cylinder and the second stage at the mouthpiece. This arrangement differs from Emile Gagnan’s and Jacques Cousteau’s original 1942 “twin-hose” design, known as the Aqua-lung, in which the cylinder’s pressure was reduced to ambient pressure in one or two or three stages which were all on the cylinder. The “single-hose” system has significant advantages over the original system.

In the “single-hose” two-stage design, the first stage regulator reduces the cylinder pressure of about 200 bar (3000 psi) to an intermediate level of about 10 bar (145 psi) The second stage demand valve regulator, connected via a low pressure hose to the first stage, delivers the breathing gas at the correct ambient pressure to the diver’s mouth and lungs. The diver’s exhaled gases are exhausted directly to the environment as waste. The first stage typically has at least one outlet delivering breathing gas at unreduced tank pressure. This is connected to the diver’s pressure gauge or computer, in order to show how much breathing gas remains.

Rebreather

An Inspiration electronic fully closed circuit rebreather

Main article: Rebreathers

Less common are closed and semi-closed rebreathers, which unlike open-circuit sets that vent off all exhaled gases, reprocess each exhaled breath for re-use by removing the carbon dioxide buildup and replacing the oxygen used by the diver.

Rebreathers release few or no gas bubbles into the water, and use much less oxygen per hour because exhaled oxygen is recovered; this has advantages for research, military, photography, and other applications. The first modern rebreather was the MK-19 that was developed at S-Tron by Ralph Osterhout that was the first electronic system.[citation needed] Rebreathers are more complex and more expensive than sport open-circuit scuba, and need special training and maintenance to be safely used.

Because the nitrogen in the system is kept to a minimum, decompressing is much less complicated than traditional open-circuit scuba systems and, as a result, divers can stay down longer. Because rebreathers produce very few bubbles, they do not disturb marine life or make a diver presence known; this is useful for underwater photography, and for covert work.

Gas mixtures

Nitrox cylinder marked up for use

Main article: Breathing gas

For some diving, gas mixtures other than normal atmospheric air (21% oxygen, 78% nitrogen, 1% trace gases) can be used, so long as the diver is properly trained in their use. The most commonly used mixture is Enriched Air Nitrox, which is air with extra oxygen, often with 32% or 36% oxygen, and thus less nitrogen, reducing the likelihood of decompression sickness. The reduced nitrogen may also allow for no or less decompression stop times and a shorter surface interval between dives. A common misconception is that nitrox can reduce narcosis, but research has shown that oxygen is also narcotic.

Several other common gas mixtures are in use, and all need specialized training. The increased oxygen levels in nitrox help fend off decompression sickness; however, below the maximum operating depth of the mixture, the increased partial pressure of oxygen can lead to oxygen toxicity. To displace nitrogen without the increased oxygen concentration, other diluents can be used, often helium, when the resultant mixture is called trimix.

For technical dives, some of the cylinders may contain different gas mixture for each phase of the dive, typically designated as Travel, Bottom, and Decompression. These different gas mixtures may be used to extend bottom time, reduce inert gas narcotic effects, and reduce decompression times.

Hazards and dangers

According to a 1970 North American study, diving was (on a man-hours based criteria) 96 times more dangerous than driving an automobile. According to a 2000 Japanese study, every hour of recreational diving is 36 to 62 times riskier than automobile driving.

Injuries due to changes in air pressure

For a full list, see Diving hazards and precautions.

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 101.3 kPa (14.7 pounds-force per square inch) 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.

If properly equalized, the sinus passages can stand the increased pressure of the water with no problems. However, congestion due to cold, flu or allergies may impair the ability to equalize the pressure. This may result in permanent damage to the eardrum. Although there are many dangers involved in scuba diving, divers can decrease the dangers through proper training and education. Open-water certification programs highlight diving physiology, safe diving practices, and diving hazards.

Effects of breathing high pressure gas

Decompression sickness

Main article: Decompression sickness

The diver must avoid the formation of gas bubbles in the body, called decompression sickness or ‘the bends’, by releasing the water pressure on the body slowly while ascending and allowing gases trapped in the bloodstream to gradually break solution and leave the body, called “off-gassing.” This is done by making safety stops or decompression stops and ascending slowly using dive computers or decompression tables for guidance. Decompression sickness must be treated promptly, typically in a recompression chamber. Administering enriched-oxygen breathing gas or pure oxygen to a decompression sickness stricken diver on the surface is a good form of first aid for decompression sickness, although fatality or permanent disability may still occur.

Nitrogen narcosis

Main article: Nitrogen narcosis

Nitrogen narcosis or inert gas narcosis is a reversible alteration in consciousness producing a state similar to alcohol intoxication in divers who breathe high pressure gas at depth. The mechanism is similar to that of nitrous oxide, or “laughing gas,” administered as anesthesia. Being “narced” can impair judgment and make diving very dangerous. Narcosis starts to affect some divers at 66 feet (20 meters). At 66 feet (20 m), Narcosis manifests itself as slight giddiness. The effects increase drastically with the increase in depth. Almost all divers are able to notice the effects by 132 feet (40 meters). At these depths divers may feel euphoria, anxiety, loss of coordination and lack of concentration. At extreme depths, hallucinogenic reaction and tunnel vision can occur. Jacques Cousteau famously described it as the “rapture of the deep”. Nitrogen narcosis occurs quickly and the symptoms typically disappear during the ascent, so that divers often fail to realize they were ever affected. It affects individual divers at varying depths and conditions, and can even vary from dive to dive under identical conditions. However, diving with trimix or heliox dramatically reduces the effects of inert gas narcosis.

Oxygen toxicity

Main article: Oxygen toxicity

Oxygen toxicity occurs when oxygen in the body exceeds a safe “partial pressure” (PPO2). In extreme cases it affects the central nervous system and causes a seizure, which can result in the diver spitting out his regulator and drowning. Oxygen toxicity is preventable provided one never exceeds the established maximum depth of a given breathing gas. For deep dives (generally past 180 feet / 55 meters), divers use “hypoxic blends” containing a lower percentage of oxygen than atmospheric air. For more information, see Oxygen toxicity.

Refraction and underwater vision

Main article: Underwater vision

A diver wearing an Ocean Reef full face mask

Water has a higher refractive index than air; it’s similar to that of the cornea of the eye. Light entering the cornea from water is hardly refracted at all, leaving only the eye’s crystalline lens to focus light. This leads to very severe hypermetropia. People with severe myopia, therefore, can see better underwater without a mask than normal-sighted people.

Diving masks and diving helmets and fullface masks solve this problem by creating an air space in front of the diver’s eyes. The refraction error created by the water is mostly corrected as the light travels from water to air through a flat lens, except that objects appear approximately 34% bigger and 25% closer in salt water than they actually are. Therefore total field-of-view is significantly reduced and eye-hand coordination must be adjusted.

(This affects underwater photography: a camera seeing through a flat window in its casing is affected the same as its user’s eye seeing through a flat mask window, and so its user must focus for the apparent distance to target, not for the real distance.)

Divers who need corrective lenses to see clearly outside the water would normally need the same prescription while wearing a mask. Generic and custom corrective lenses are available for some two-window masks. Custom lenses can be bonded onto masks that have a single front window.

A “double-dome mask” has curved windows in an attempt to cure these faults, but this causes a refraction problem of its own.

Commando frogmen concerned about revealing their position when light reflects from the glass surface of their diving masks may instead use special contact lenses to see underwater.

As a diver descends, he must periodically exhale through his nose to equalize the internal pressure of the mask with that of the surrounding water. Swimming goggles are not suitable for diving because they only cover the eyes and thus do not allow for equalization. Failure to equalise the pressure inside the mask may lead to a form of barotrauma known as mask squeeze.

Controlling buoyancy underwater

Diver under the Salt Pier in Bonaire.

To dive safely, divers must control their rate of descent and ascent in the water. Ignoring other forces such as water currents and swimming, the diver’s overall buoyancy determines whether he ascends or descends. Equipment such as the diving weighting systems, diving suits (Wet, Dry & Semi-dry suits are used depending on the water temperature) and buoyancy compensators can be used to adjust the overall buoyancy. When divers want to remain at constant depth, they try to achieve neutral buoyancy. This minimizes gas consumption caused by swimming to maintain depth.

The downward force on the diver is the weight of the diver and his equipment minus the weight of the same volume of the liquid that he is displacing; if the result is negative, that force is upwards. Diving weighting systems can be used to reduce the diver’s weight and cause an ascent in an emergency. Diving suits, mostly being made of compressible materials, shrink as the diver descends, and expand as the diver ascends, creating buoyancy changes. The diver can inject air into some diving suits to counteract the compression effect and squeeze. Buoyancy compensators allow easy and fine adjustments in the diver’s overall volume and therefore buoyancy. For open circuit divers, changes in the diver’s lung volume can be used to adjust buoyancy.

Avoiding losing body heat

Dry suit for reducing exposure

Main article: Diving suit

Water conducts heat from the diver 25 times better than air, which can lead to hypothermia even in mild water temperatures. Symptoms of hypothermia include impaired judgment and dexterity, which can quickly become deadly in an aquatic environment. In all but the warmest waters, divers need the thermal insulation provided by wetsuits or drysuits.

In the case of a wetsuit, the suit is designed to minimize heat loss. Wetsuits are generally made of neoprene that has small gas cells, generally nitrogen, trapped in it during the manufacturing process. The poor thermal conductivity of this expanded cell neoprene means that wetsuits reduce loss of body heat by conduction to the surrounding water. The neoprene in this case acts as an insulator.

The second way in which wetsuits reduce heat loss is to trap a thin layer of water between the diver’s skin and the insulating suit itself. Body heat then heats the trapped water. Provided the wetsuit is reasonably well-sealed at all openings (neck, wrists, legs), this reduces water flow over the surface of the skin, reducing loss of body heat by convection, and therefore keeps the diver warm (this is the principle employed in the use of a “Semi-Dry”)

Spring suit and steamer

In the case of a drysuit, it does exactly that: keeps a diver dry. The suit is sealed so that frigid water cannot penetrate the suit. Drysuit undergarments are often worn under a drysuit as well, and help to keep layers of air inside the suit for better thermal insulation. Some divers carry an extra gas bottle dedicated to filling the dry suit. Usually this bottle contains argon gas, because of its better insulation as compared with air.

Drysuits fall into two main categories neoprene and membrane; both systems have their good and bad points but generally their thermal properties can be reduced to:

Membrane: usually a trilaminate construction; owing to the thinness of the material (around 1 mm), these require an undersuit, usually of high insulation value if diving in cooler water.

Neoprene: a similar construction to wetsuits; these are often considerably thicker (78 mm) and have sufficient insulation to allow a lighter-weight undersuit (or none at all); however on deeper dives the neoprene can compress to as little as 2 mm thus losing a proportion of their insulation. Compressed or crushed neoprene may also be used (where the neoprene is pre-compressed to 23 mm) which avoids the variation of insulating properties with depth.

Avoiding skin cuts and grazes

Diving suits also help prevent the diver’s skin being damaged by rough or sharp underwater objects, marine animals or coral.

Diving longer and deeper safely

There are a number of techniques to increase the diver’s ability to dive deeper and longer:

Technical diving diving deeper than 40 metres (130 ft), using mixed gases, and/or entering overhead environments (caves or wrecks)

surface supplied diving use of umbilical gas supply and diving helmets.

saturation diving long-term use of underwater habitats under pressure and a gradual release of pressure over several days in a decompression chamber at the end of a dive.

Being mobile underwater

The diver needs to be mobile underwater. Streamlining dive gear will reduce drag and improve mobility. Personal mobility is enhanced by swimfins and Diver Propulsion Vehicles. Other equipment to improve mobility includes diving bells and diving shots.

Scuba dive training and certification agencies

Main article: List of diver training organizations

Diving lessons in Monterey Bay, California

Recreational scuba diving does not have a centralized certifying or regulatory agency, and is mostly self regulated. There are, however, several large diving organizations that train and certify divers and dive instructors, and many diving related sales and rental outlets require proof of diver certification from one of these organizations prior to selling or renting certain diving products or services.

The largest international certification agencies that are currently recognized by most diving outlets for diver certification include:

American Canadian Underwater Certifications (ACUC) (formerly Association of Canadian Underwater Councils) originated in Canada in 1969 and expanded internationally in 1984

British Sub Aqua Club (BSAC) based in the United Kingdom, founded in 1953 and is the largest dive club in the world

European Committee of Professional Diving Instructors (CEDIP) based in Europe since 1992 (see Cedip on French Wiki pages)

Confdration Mondiale des Activits Subaquatiques (CMAS), the World Underwater Federation

National Association of Underwater Instructors (NAUI) based in the United States

Professional Diving Instructors Corporation (PDIC) based in the United States

Professional Association of Diving Instructors (PADI) based in the United States, largest recreational dive training and certification organization in the world

Scottish Sub Aqua Club (SSAC or ScotSAC) the National Governing Body for the sport of diving in Scotland.

International Training SDI, TDI & ERDi -based in the United States, TDI is the world’s largest technical diving agency, SDI is the recreational division focusing on new methods and online courses, and ERDi is the public safety component.

Scuba Schools International (SSI) based in the United States with 35 Regional Centers and Area Offices around the globe.

YMCA scuba based in the U.S., part of Young Men’s Christian Association (YMCA), a Christian related organization (open to all faiths, ages and genders despite the historic name)

See also

Altitude diving

Aqualung, a type of breathing set

Aquanaut

Barodontalgia

Barotrauma

British Sub-Aqua Club

Coral Cay Conservation

Decompression sickness

Diver training

Divers Alert Network (DAN)

Diving equipment

Diving hazards and precautions

Diving physics

Diving signal

Diving suit

Drift diving

Engineer Diver

Like-A-Fish, a breathing set that extracts oxygen from surrounding water

scuba diving quarry

Sea Hunt, a television fiction series about scuba diving

Sea Trek

Snorkeling

Snuba

Technical diving

Timeline of underwater technology

Underwater diving

Underwater photography

Underwater videography

Wreck diving

Reference list

Scuba diving, grouped

^ “Compact Oxford English Dictionary – scuba”. Oxford University Press. http://www.askoxford.com/concise_oed/scuba?view=uk. 

^ a b c d e f g h i j US Navy Diving Manual, 6th revision. United States: US Naval Sea Systems Command. 2006. http://www.supsalv.org/00c3_publications.asp?destPage=00c3&pageID=3.9. Retrieved 2008-04-24. 

^ a b c d e f g h i j k Brubakk, Alf O; Neuman, Tom S (2003). Bennett and Elliott’s physiology and medicine of diving, 5th Rev ed. United States: Saunders Ltd. p. 800. ISBN 0702025712. 

^ Vann RD (2004). “Lambertsen and O2: beginnings of operational physiology”. Undersea Hyperb Med 31 (1): 2131. PMID 15233157. http://archive.rubicon-foundation.org/3987. Retrieved 2008-04-25. 

^ Butler FK (2004). “Closed-circuit oxygen diving in the U.S. Navy”. Undersea Hyperb Med 31 (1): 320. PMID 15233156. http://archive.rubicon-foundation.org/3986. Retrieved 2008-04-25. 

^ Hirschl, RB; et al (1995). “Liquid ventilatory in adults, children, and full-term neonates”. Lancet 346: 12011202. doi:10.1016/S0140-6736(95)92903-7. 

^ Sekins, KM; et al (1999). “Recent innovation in total liquid ventilation system and component design”. Biomedical instrumentation and technology 33: 277284. PMID 10360218. 

^ a b Richardson, D; Menduno, M; Shreeves, K. (eds). (1996). “Proceedings of Rebreather Forum 2.0.”. Diving Science and Technology Workshop.: 286. http://archive.rubicon-foundation.org/7555. Retrieved 2008-08-20. 

^ Hesser, CM; Fagraeus, L; Adolfson, J (1978). “Roles of nitrogen, oxygen, and carbon dioxide in compressed-air narcosis.”. Undersea Biomed. Res. 5 (4): 391400. ISSN 0093-5387. OCLC 2068005. PMID 734806. http://archive.rubicon-foundation.org/2810. Retrieved 2008-04-08. 

^ Brubakk, Alf O; Neuman, Tom S (2003). Bennett and Elliott’s physiology and medicine of diving, 5th Rev ed. United States: Saunders Ltd. p. 304. ISBN 0702025712. 

^ Deaths During Skin and Scuba Diving in California in 1970

^ Is recreational diving safe?, por Ikeda, T y Ashida, H

^ Longphre, J. M.; P. J. DeNoble; R. E. Moon; R. D. Vann; J. J. Freiberger (2007). “First aid normobaric oxygen for the treatment of recreational diving injuries”. Undersea Hyperb Med. 34 (1): 4349. ISSN 1066-2936. OCLC 26915585. PMID 17393938. http://archive.rubicon-foundation.org/5514. Retrieved 2008-05-03. 

^ NOAA Diving Manual, 4th Edition, Best Publishing, 2001

^ “Thermal Conductivity”, Georgia State University, accessed 15 February 2008

^ Weinberg, R. P.; E. D. Thalmann. (1990). “Effects of Hand and Foot Heating on Diver Thermal Balance”. Naval Medical Research Institute Report 90-52. http://archive.rubicon-foundation.org/4247. Retrieved 2008-05-03. 

^ Nuckols ML, Giblo J, Wood-Putnam JL. (September 1518, 2008). “Thermal Characteristics of Diving Garments When Using Argon as a Suit Inflation Gas.”. Proceedings of the Oceans 08 MTS/IEEE Quebec, Canada Meeting (MTS/IEEE). http://archive.rubicon-foundation.org/7962. Retrieved 2009-04-17. 

Further reading

Books published by the British Sub-Aqua Club:

The Diving Manual, BSAC, ISBN 0-9538919-2-5

Dive Leading, BSAC, ISBN 0-9538919-4-1

The Club 1953-2003, BSAC, ISBN 0-9538919-5-X

Free Scuba textbook by George D. Campbell, III called Diving With Deep-Six

External links

Divers Alert Networkiving Emergencies/Hyperbaric Chamber Assistance

Scuba diving travel guide from Wikitravel

Divemaster.com large forum and news and information site

Skaphandrus.comnline Scuba Diving Information

v  d  e

Underwater diving

Types:

Scuba diving  Surface supplied diving  Free-diving  Snorkelling  Saturation diving

Specialities:

Technical diving  Deep diving  Decompression diving  Mixed gas diving  Wreck diving  Cave diving  Ice diving  Rebreather diving  Solo diving  Altitude diving

Equipment:

Diving suit  Scuba set  Rebreather  Dive computer  Diver propulsion vehicle  Mask  Fins  Snorkel  Buoyancy control device

Disciplines:

Professional diving  Police diving  Military diving  Underwater photography  Underwater videography

Hazards:

Decompression sickness  Nitrogen narcosis  Oxygen toxicity  Barotrauma  Hyperbaric medicine  Drowning  Shallow water blackout  Deep water blackout  High pressure nervous syndrome  Dysbaric osteonecrosis

Categories: Underwater diving | Mixed sports | B-Class Water sports articlesHidden categories: Wikipedia semi-protected pages | All articles with unsourced statements | Articles with unsourced statements from February 2009 | Articles lacking in-text citations from February 2008 | All articles lacking in-text citations

Beautiful Film of Scuba Diving in a Newly-Flooded Meadow.Hiking trails, picnic tables, benches and signs all under water in this very relaxing video filmed in Austria. See more at swift-move.com The “Grüner See” (engl. Green Lake) is situated in upper styria, austria (see geotag). It is amazingly beautiful because of its deep green colour and the surrounding alpine scenery. The lake itself dries up in autumn but fills up with melting water. The water itself of the lake is extremely pure, like glass. The colour is a result of light refraction. “The night before there seemed to be heavy rain and too much of the pollen were flushed in the water and were floating. So the visibility could be much better, i´ve missed the „crystal clear water. You have to know the Green Lake is famous for its clear water. The good thing for this day was the water level with 9,40m. Spring flowers, plants, benches, hiking trails were below the surface. And i have found out when its the best time during the two to three months “flood” to get in the water – i was to early in this season. Altough the water temperature was between 5 and 6 degrees Celcius i did two dives (85 and 96 minutes long) My face was well frozen, i can hardly speak afterwards. I hoped this procedure kept my face young and skintight. After watching the footage it seemed to be different.” The beautiful music is by “Tabolomegalo”