Scuba diving
SCUBA is an acronym for Self Contained Underwater Breathing Apparatus. In short, scuba diving is an underwater activity practiced with the help of a system or an apparatus (usually a tank and air pressure regulator) able to provide a reserve of gas (usually air) in order to allow the diver to breathe air during the immersion.
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See also Timeline of underwater technology.
The first known use of air tanks is in Italy, 15th century: Leonardo da Vinci affirmed in his Atlantic Codex (Biblioteca Ambrosiana, Milan) that systems were used at that time to artificially breathe under water, but he did not explain them in detail due to what he described as "bad human nature", that would have taken advantage of this technique to sink ships and even commit murders. Some drawings, however, showed different kinds of snorkels and an air tank (to be carried on the breast) that presumably should have no external connections. Other drawings showed a complete immersion kit, with a plunger suit which included a sort of mask with a box for air. The project was so detailed that it included a urine collector, too.
After Leonardo's studies, and those of Halley (yes, the astronomer), in the 19th century August Siebe invented a sort of apparatus but still not completely independent of external air. His stu
dies were perfected by the Frenchman Cabirol and later, more incisively, by Rouquayrol and Denayrouze, who added the first modern air tank.
In 1906 the first decompression tables ("quote decompression method") were released.
In 1915 Sir Robert Davis invented the "Submarine escape apparatus", by which a compressed oxygen bottle could be opened in water in case of need, sending air to mouth. Used air could be then expelled to a filtering "false lung" from where it is finally lost.
In 1925 Le Prieur invented another better developed apparatus in 1933, working with compressed air. It could permit a 20 minute stay at -7 meters and 15 minutes at -15 (these data appear however to be re-checked).
In 1941, during WWII, these experimental apparatuses were used for one of the best known and most spectacular war actions: Italian "Decima Mas" (elite navy corps at the orders of commander Junio Valerio Borghese) entered at nighttime the port of Alexandria, Egypt, in immersion. They used special underwater vehicles ("maiali" = pigs) and breathing apparatus, and were able to silently attach miness on the bottom of the ships, that later were effectively sunk.
In July of 1943 the Frenchman Georges Comheines was able to reach -53 meters (~174 feet), off the coast of Marseille, with a two-bottles apparatus he had developed from Le Prieur's one. Immersion lasted 2 minutes (apparently out of decompression tables).
In the following October, Frédéric Dumas reached -62 meters (~200 feet), with the apparatus co-invented by Jacques Cousteau and Emile Gagnan and named Aqua-lung.
In 1958 the TV series SEA HUNT, introduced SCUBA diving to the TV audience.
Movies have also popularized the sport. SCUBA diving is featured in many James Bond films.
The maximum safe depth for normal scuba gear with normal air in the tank is certainly within 50 meters (~150 feet), beyond which nitrogen narcosis becomes an almost certain danger. Onset of narcosis is dependent on the workload, the physical conditions, and training of the diver but also depends on variable gas concentration in blood and lungs, that might change very suddenly with minimum changes of vertical speed (descent). Risk factors are different for each individual, and cannot therefore be reliably foreseen: the appearance of narcosis can be very rapid and faster than the capability of the diver to recognize it. Narcosis will also disappear once you ascend to shallower depth.
It is vital to remember that an accident can occur even in the very first meter of immersion, depending on personal conditions and hazards; every statistical report about accidents demonstrate that claimed "safe ranges" are nothing more than a rough recording of some data (episodically and not organically collected) with no scientific confirmation.
Diving can be an experience capable of producing unique emotions, but only with complete respect of safety rules. Any accident in water, even the "lightest" one, can bring to death to the untrained diver. The rising numbers of deaths in the early years of scuba forced training organisations of come up with minimum standards of training.
Some say that it could be possible to learn how to tolerate narcosis (allegedly, same as with alcohol), but disconcerting doubts cannot allow this statement to be released so easily without at least the mention that nothing and no one can seriously ensure that you will be able to reach again the surface if a similar accident happens, effective known rescues generally having depended on highly hazardous and quite randomized factors.
If Enriched Air Nitrox is used, additional serious risks come from oxygen toxicity. Diving on pure oxygen becomes toxic at a depth of merely 10 ft. Breathing mixes become dangerous when the partial pressure of oxygen reaches 1,4-1,6 bar. Some people consider 1,2 bar dangerous pressure (and some others suggest never passing 0,9), that is reached at a very early depth.
Relatively "safe" deep dives over 70 meters (~210 feet) can be done by well experienced divers using Heliox or Trimix gas mixes. As with Enriched Air Nitrox, special training is obligatory. These depths are however in a range that could recommend a boat-assisted immersion for a different air provision system, such as pneumatic pumps on surface.
Scuba diving requires training, and nobody should consider attempting to dive without professional instruction. Even experienced divers should never dive alone, but instead have a companion (or more) in sight.
Major deadly risk factors include:
History
Nitrogen Narcosis Information
Major diving diseases include:
"Decompression sickness" ("the bends") is caused by ascending from deep depths too quickly. Nitrogen from the air breathed dissolves in the blood at depth, and as the diver ascends, the nitrogen is released from the blood and forms bubbles throughout the diver's bloodstream, with painful and often fatal results. The prevention is to surface slowly from all dives, so that nitrogen can "de-gass" from the diver's blood without forming bubbles. Divers also ensure adequate de-gassing by performing one or more "safety stops" after long or deep dives, in which the diver hovers at a prescribed depth for a prescribed amount of time before actually surfacing. Dive Tables (and dive computers which use the tables) are used to calculate maximum bottom time, and recommend additional safety stops.Things to do underwater
In most situations cummunications is facilitated with the use of simple hand signals. The most basic ones: Thumbs up = lets go up, thumbs down = lets go down, circle with thumb and index finger = I'm OK. Are you OK?, "cutting" throat with a flat hand = I'm out of air, wobbling a flat hand = something is wrong.
The focused beam of a torch can be used for basic signalling as well. Drawing a circle on the ground in front of buddy = the OK signal, waving the torch = attention please!
When using special equipment, voice can be used for communication. Equipment usually consists of a full face mask with a submergible microphone and speaker and either a hard wired telepone-like setup or a thru-water supersonic radio-like system.
Scuba Glossary
; Skin: a lycra suit worn by a diver in warm water or under a wet suit.
; Surface interval: the time between dives. divers need to track this time interval for planning the next dive.
; Time to fly: Divers must wait approx. 24 hours after the last dive before flying.
; Wall diving : Scuba diving along the face of a vertical wall
; Shore diving: Scuba diving that starts from the shore line
; Buddy System: Two divers that dive together as a team for safety
; Trash dive: a dive dedicated to removing trash from the underwater environment
; Divemaster: A professional level diver who is in charge of the dive.
; Beach master: A person on the beach who records when divers enter and exit the water. Typically used during scuba classes to keep track of the students, watch the gear, provide assistance when required.
; C-card: Certification card (proof of training or experience)
; Log Book: List of the dives a diver has recorded for proof of experience.
; Dive Tables: Give the maximum times that can be spent at depth, and pauses needed during ascent, before Decompression sickness becomes a danger.
; Navy Tables : A set of dive tables developed by the US Navy. Used by early divers as a method to determine maximum time and depth.
; Dive Shop : supplier of dive equipment or training, or organizer of dive expeditions.
; Dive Flag: Flag used by a boat to indicate that it has 'divers down'.
; Hard Hat diving: A term for commercial divers
; Dive club: a group of people with an interest in SCUBA diving
; Navy SEAL: A highly trained military diver (http://www.sealchallenge.navy.mil/ )
; Frogman: A slag term for scuba divers
; Fire Diving: An urban legend about a diver who is scooped up by a plane/chopper and dropped on a forest fire led someone to build a web site for the fictitious sport of Firediving
Becoming a scuba diver requires training. Dive training organisations can be found throughout the world, and in very large numbers in popular dive spots. A good dive training organisation will always offer courses to the standard of a recognised certification organisation, such as those listed below. Many dive shops in popular holiday locations offer courses that can teach you to dive in a few days, and can be combined with your vacation.
Initial training can be broken down into three phases.
Many of the activities mentioned above require additional training to be done safely.
Certifying dive organizations include:
Training and Certification
Upon completing the course the student is issued a certification card.Other organizations:
Other: ACUC, ANIS, CEDIP, DIWA, ESA, FIAS, FIPS, IADS, IAHD, IDD, NASE, PDA, PSA, SUSV, TDI, TSA, VDST, VDTL, VIT, YMCA, ÖSPVExternal links
Popular locations for SCUBA diving
Equipment Manufacturers
Equipment used in scuba diving
A diver in a pool wearing a full face mask from AGA and a twin 6 liter 300 bar tank rig.
All modern regulators consists of two stages. The first stage attaches to the tank and reduces the tank pressure to aprox. 1 MPa obove ambient pressure. This intermediate pressure gas is lead thru a hose to the second stage witch in turn reduces the gas pressure to ambient pressure.
Earlier models of regulators had the two stages combined into one. Air was supplied to the diver via a large corrugated hose to the divers mouth piece. Exhaled gas returned via a second hose back to the regulator where it was released into the water.
Works just as the "dry" versions. Often worn on the forearm, just as a clock.Movies that feature Scuba Diving
Scuba Magazines
