Scuba diving ("scuba" originally being an acronym for Self Contained Underwater Breathing Apparatus , although now widely considered a word in its own right) is a form of underwater diving in which a diver uses a scuba set to breathe underwater for recreation, commercial or industrial reasons.
Unlike early diving, which relied exclusively on air pumped from the surface, scuba divers carry their own source of breathing gas (usually compressed air), allowing them greater freedom than with an air line. Both surface supplied and scuba diving allow divers to stay underwater significantly longer than with breath-holding techniques as used in snorkelling and free-diving.
According to the purpose of the dive, a diver usually moves underwater by swimfins attached to his feet, but external propulsion can come from an underwater vehicle, or a sled pulled from the surface.
History
Main article: timeline of underwater technologyThe 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 S elf- C ontained U nderwater B reathing A pparatus ) 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 word— scuba . It has become acceptable to refer to "scuba equipment" or "scuba apparatus"—examples of the linguistic RAS syndrome.
Types of diving
See also: Recreational diving and Professional divingScuba 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:
Breathing underwater
For more information, see Diving regulator.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. Some experiments indicate the possibility of filling and ventilating artificially the lungs with a dedicated liquid (Liquid breathing) — this currently has only medical applications.
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 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
Main article: RebreathersLess common are closed and semi-closed rebreathers, which unlike open-circuit sets, which 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. Rebreathers are more complex and more expensive than sport open-circuit scuba, and need special training and maintenance to be safely used.
Gas mixtures
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.
In cases of technical dives, some of the cylinders may cont
SCUBA diving - SCUBA diving holidays and information :: scubadiving.co ...
Check here for information on scuba diving. Whether you want to go on a scuba diving holiday, or are looking for equipment or information on certification, we have plenty of ...
Scuba Diving Holidays & PADI Courses | Center Parcs
Learn how to dive safely in the Center Parcs Subtropical Swimming Paradise under the tuition of the Center Parcs expert P.A.D.I instructors.
Global Scuba: Diving holiday Oman, NAUI & PADI courses Oman, Scuba ...
The best diving in Muscat. We offer full range of NAUI Scuba Diver & PADI courses with scuba diving holiday packages in Oman. We also have diving gear equipments available for rent
SCUBA DIVING HOLIDAYS
Scuba Diving Holidays to the Red Sea and Beyond
Scuba Diving Holiday Offers with Neilson Active Holidays
Explore Neilson s wide range of diving package holidays and scuba diving holidays in the Mediterranean. View or book online now!
scuba diving holidays from Planet Dive
red sea diving holidays and world wide liveaboard safaris. Search Scubasnacks for the best package deals.
Scuba Diving Travel | Discount Dive Holiday Packages - Scuba Diving ...
ScubaDiveTravel.co.uk has Discount Dive Travel Packages! Dive Resort Reviews for the Best Scuba Destinations, and the Top 10 Dive Resorts in the world!
Maldives Dive Travel - Best price maldives liveaboard scuba diving ...
Book your Maldives diving safari holiday online. Best price offers, 15 years of experience and the biggest selection of safari ships in the Maldives.
SCUBA DIVING HOLIDAYS
Scuba Diving Holidays Worldwide and Red Sea Liveaboards
PADI 5 star IDC Centre | Scuba Diving Lessons | Training Courses in ...
PADI 5 star IDC Centre | Scuba Diving Training Courses in Essex - Try scuba diving lessons for children and families