Monday, October 22, 2012

Open Water Diver Skills~ "For SCUBA Diving"


Open Water Diver Skills  for SCUBA Diving.


Scuba diving is a mode of underwater diving in which a scuba diver uses a self-contained underwater breathing apparatus (scuba) to breathe underwater.[1]

Unlike other modes of diving, which rely either on breath-hold or on breathing gas pumped from the surface, scuba divers carry their own source of breathing gas, usually compressed air,[2] allowing them greater freedom of movement than with an air line or diver's umbilical and longer underwater endurance than breath-hold.

Scuba equipment may be open circuit, in which exhaled gas is expelled to the surroundings, or a closed or semi-closed circuit rebreather, in which the breathing gas is scrubbed to remove carbon dioxide, and the oxygen used is replenished from a supply of feed gas before being re-breathed.

Scuba diving may be done recreationally or professionally in a number of applications, including scientific, military and public safety roles, but most commercial diving uses surface supplied diving equipment when this is practicable.

A scuba diver primarily moves underwater by using fins attached to the feet, but external propulsion can be provided by a diver propulsion vehicle, or a sled pulled from the surface.

Other equipment includes a dive mask to improve underwater vision, a protective dive suit, equipment to control buoyancy, and equipment related to the specific circumstances and purpose of the dive.

Scuba divers are trained in the procedures and skills appropriate to their level of certification by instructors affiliated to the diver certification organisations which issue these certifications.

These include standard operating procedures for using the equipment and dealing with the general hazards of the underwater environment, and emergency procedures for self-help and assistance of a similarly equipped diver experiencing problems.

A minimum level of fitness and health is required by most training organisations, but a higher level of fitness may be appropriate for some applications.


 
Recreational scuba diver.


Origins

Original Aqualung scuba set.
1: Air Hose, 2: Mouthpiece, 3: Regulator, 4: Harness, 5: Back plate, 6: Tank
 
 
By the early twentieth century, two basic systems for scuba (self-contained underwater breathing apparatus) had emerged: open-circuit scuba where the diver's exhaled breath is vented directly into the water, and closed-circuit scuba where the carbon dioxide is removed from the diver's exhaled breath which has oxygen added and is recirculated.

Rebreathers

The closed-circuit rebreathers were first developed for escape and rescue purposes, and were modified for military use, due to their stealth advantages, as they produce very few bubbles.

The first commercially successful closed-circuit scuba was designed and built by English diving engineer, Henry Fleuss in 1878, while working for Siebe Gorman in London.[3][4]

His SCBA (self-contained breathing apparatus) consisted of a rubber mask connected to a breathing bag, with (estimated) 50-60% O2 supplied from a copper tank and CO2 scrubbed by rope yarn soaked in a solution of caustic potash; the system giving a duration of about three hours.[4][5]

Sir Robert Davis, head of Siebe Gorman, perfected the oxygen rebreather in 1910[4][6] with his invention of the Davis Submerged Escape Apparatus, the first practical rebreather to be made in quantity.[7]

Rebreathers have been increasingly used by civilians for recreation, especially since the end of the Cold War.

This reduced the perceived risk of attack by Communist Bloc forces, including by their combat divers.[clarification needed]

After that, the world's armed forces had less reason to requisition civilian rebreather patents, and automatic and semi-automatic recreational diving rebreathers started to appear.[citation needed]

Open-circuit scuba

The first commercially successful scuba sets were the Aqualung twin hose open-circuit units developed by Emile Gagnan and Jacques-Yves Cousteau in 1943, in which compressed air carried in back mounted cylinders is inhaled through a demand regulator and then exhaled into the water adjacent to the tank.[8]

The single hose two stage scuba regulators trace their origins to Australia, where Ted Eldred developed the first example of this type of regulator, known as Porpoise scuba gear.

This was developed because patents protected the Aqualung's twin hose design.[citation needed]

The single hose regulator separates the demand valve from the cylinder, giving the diver air at the ambient pressure at the mouth, rather than ambient pressure at the top of the cylinder.

Etymology

The term "SCUBA" (an acronym for "self-contained underwater breathing apparatus") originally referred to United States combat frogmen's oxygen rebreathers, developed during World War II by Christian J. Lambertsen for underwater warfare.[2][9][10]

"SCUBA" was originally an acronym, but is now generally used as a common noun or adjective, "scuba".[11]

It has become acceptable to refer to "scuba equipment" or "scuba apparatus"—examples of the linguistic RAS syndrome.

Applications of scuba diving

Shooting underwater video on scuba
 
 


Scuba diving may be performed for a number of reasons, both personal and professional.


Recreational diving 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. Some of these tasks are suitable for scuba.[1][12][13]

There are divers who work, full or part-time, in the recreational diving community as instructors, assistant instructors, divemasters and dive guides.

In some jurisdictions the professional nature, with particular reference to responsibility for health and safety of the clients, of recreational diver instruction, dive leadership for reward and dive guiding is recognized and regulated by national legislation.[13][14]

Other specialist areas of scuba 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, paramedical service or lifeguard unit, and may be classed as public service diving.[13]

Lastly, there are professional divers involved with underwater environment, such as underwater photography or underwater videography divers, who document the underwater world, or scientific diving, including marine biology, geology, hydrology, oceanography and underwater archaeology.[12][13]

The choice between scuba and surface supplied diving equipment is based on both legal and logistical constraints.

Where the diver requires mobility and a large range of movement, scuba is usually the choice if safety and legal constraints allow.

Higher risk work, particularly in commercial diving, may be restricted to surface supplied equipment by legislation and codes of practice.[15][16]

Diving activities commonly associated with scuba include:

Source:Wikipedia.org

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