Portal:Underwater diving

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Underwater diving

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Underwater diving is the practice of going underwater, either with breathing apparatus (scuba diving and surface supplied diving) or by breath-holding.

Recreational diving is a popular activity (also called sports diving or subaquatics), and includes technical diving, recreational scuba diving, freediving, snuba, snorkeling and a range of competitive sports performed underwater.

Professional diving includes diving as part of one's occupation, and takes a range of diving activities to the underwater work site. Commercial diving, military diving, public safety diving and scientific diving are aspects of professional diving.

Freediving is a form of underwater diving that does not involve the use external breathing devices, but relies on a diver's ability to hold his or her breath until resurfacing. Activities include breath-hold spear fishing, freedive photography, apnea competitions, and to some degree, snorkeling.

The scope of this portal includes the technology supporting diving activities, the physiological and medical aspects of diving, the procedures of diving, underwater activities which are to some degree dependent on diving, economical and commercial aspects of diving, biographical information on notable divers, inventors and manufacturers of diving related equipment and researchers into aspects of diving,

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Divers using the anchor cable as an aid to depth control during a decompression stop

The practice of decompression by divers comprises the planning and monitoring of the profile indicated by the algorithms or tables of the chosen decompression model, the equipment available and appropriate to the circumstances of the dive, and the procedures authorised for the equipment and profile to be used. There is a large range of options in all of these aspects.

Decompression in the context of diving derives from the reduction in ambient pressure experienced by the diver during the ascent at the end of a dive or hyperbaric exposure and refers to both the reduction in pressure and the process of allowing dissolved inert gases to be eliminated from the tissues during this reduction in pressure.

When a diver descends in the water column the ambient pressure rises. Breathing gas is supplied at the same pressure as the surrounding water, and some of this gas dissolves into the diver's blood and other fluids. Inert gas continues to be taken up until the gas dissolved in the diver is in a state of equilibrium with the breathing gas in the diver's lungs, (see: "Saturation diving"), or the diver moves up in the water column and reduces the ambient pressure of the breathing gas until the inert gases dissolved in the tissues are at a higher concentration than the equilibrium state, and start diffusing out again.

Dissolved inert gases such as nitrogen or helium can form bubbles in the blood and tissues of the diver if the partial pressures of the dissolved gases in the diver gets too high when compared to the ambient pressure. These bubbles and products of injury caused by the bubbles, can cause damage to tissues known as decompression sickness or the bends. The immediate goal of controlled decompression is to avoid development of symptoms of bubble formation in the tissues of the diver, and the long term goal is to also avoid complications due to sub-clinical decompression injury.

Decompression may be continuous or staged, where the ascent is interrupted by stops at regular depth intervals, but the entire ascent is part of the decompression, and ascent rate can be critical to harmless elimination of inert gas. What is commonly known as no-decompression diving, or more accurately no-stop decompression, relies on limiting ascent rate for avoidance of excessive bubble formation.

The procedures used for decompression depend on the mode of diving, the available equipment, the site and environment, and the actual dive profile. Standardised procedures have been developed which provide an acceptable level of risk in the circumstances for which they are appropriate. Different sets of procedures are used by commercial, military, scientific and recreational divers, though there is considerable overlap where similar equipment is used, and some concepts are common to all decompression procedures.

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Colonel William Paul "Bill" Fife USAF (Ret) (November 23, 1917 – October 13, 2008) was a United States Air Force officer that first proved the feasibility for U.S. Air Force Security Service airborne Communications Intelligence (COMINT) collection and Fife is considered the "Father of Airborne Intercept". Fife was also a hyperbaric medicine specialist who was known for his pioneering research on pressurized environments ranging from high altitude to underwater habitats. Fife was a Professor Emeritus at Texas A&M University and was instrumental in the founding of the American Academy of Underwater Sciences.

Fife was a pioneer in undersea medicine and served as director of the Texas A&M University Hyperbaric laboratory.

He was active with the HydroLab saturation diving research program funded by the National Oceanic and Atmospheric Administration, and was an aquanaut, having spent 28 days in saturation in the habitat performing physiology experiments.

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Japan Aerospace Exploration Agency (JAXA) astronaut Soichi Noguchi, Expedition 22/23 flight engineer, attired in a training version of his Extravehicular Mobility Unit (EMU) spacesuit, participates in a spacewalk training session in the waters of the Neutral Buoyancy Laboratory (NBL) near NASA's Johnson Space Center. Divers are in the water to assist Noguchi in his rehearsal, which is intended to help prepare him for work on the exterior of the International Space Station


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