The sea has always been a precious source for mankind, not only of food, but also of precious materials and objects such as pearls. The desire to dive deeper and longer has therefore probably always inhabited man. Some societies, such as the Bajau of Indonesia, have physiological and genetic adaptations that increase their performance in apnea.
Why was scuba diving invented
Commander Jacques Cousteau was a pioneer of modern scuba diving. During the Second World War, after the 1940 armistice, Simone and Jacques-Yves Cousteau’s family met the Ichac family in Megeve, France. Cousteau and Marcel Ichac shared the same desire to introduce the general public to unknown and inaccessible places: for the former, it was the underwater world, for the latter, it was the high mountains.
Cousteau and Emile Gagnan worked together to develop a regulator that automatically delivers compressed air even when inhaled slightly. Until that time, all other devices supplied air continuously or a valve had to be opened and closed continuously. For unknown reasons, the principle of the demand-controlled regulator developed by Rouquayrol and Denayrouse in the 19th century was never pursued further.
Costeau and Gagnan provided their regulator with hoses and a mouthpiece and attached it to two compressed air bottles. In January 1943 this development was tested by Costeau in the cold Marne (river near Paris). After a modification (inhalation and exhalation valves were brought to the same height) they patented the “Aqua Lung”…
From Jacques Cousteau work the technological advances in compressed air pumps, carbon dioxide absorbing agents and regulators have also made it possible for people to remain submerged for a long time.
The different types of diving
The desire to explore the seas was another reason why was scuba diving invented. There are four different methods of diving, with the diving equipment as we know it today.
a. Stop by Air (Apnea, Snorkeling):
This earliest form of diving is still used as a sport and for commercial purposes. The air-filled cavities of the apnea-diver (eg lung) are strongly compressed by the increasing water pressure during the descent. These dives are limited by the personal breath-holding ability and the risk of drowning due to hypoxia. Usually the times are one minute or less.
b. Dives in pressurized cabins with atmospheric pressure
Source: Effects of Pressure on Divers
The thick walls of these units withstand the pressure of the water. As a result, a cabin pressure corresponding to sea level height (one atmosphere, 1 bar) can be maintained inside. This prevents the negative effects of increasing ambient pressure on the occupants.
Examples of such devices are:
– The Bathysphere, a “hollow steel ball” without its own drive, which is lowered by a cable from the mothership
– The bathyscaph with its own taring control – no cable is needed for the ascent and ascent
– Submarines capable of covering large distances in any direction by their own propulsion
All of these devices require a system that provides both fresh breath (usually by adding oxygen to the existing air) and also absorbs the exhaled carbon dioxide (eg, soda lime, lithium hydroxide, or similar compounds that absorb CO 2 ). A modern advancement of this technique is the independent, armored diving suit. The diver is agile and able to withstand the ambient pressure in depth. The diver turns themselves into a small submarine and can work for hours at a depth of several hundred feet.
c. Dives with compressed air supply from the surface:
The fresh air supply is separate from the diver and located on the surface. Air is supplied via a long umbilical cord, which ends in its simplest form in a mouthpiece at the diver. In better systems, the hose will go into the dive suit or into larger spaces where personnel are staying. Devices of this type are used in so-called caissons (used in bridge work, or tunnel), underwater stations, diving bells and helmet diving equipment. In all of these devices, the diver exhales air at a pressure equal to the ambient pressure of the water. As a result, problems with decompression (bends, air embolism, etc.) are possible if the climb is too fast. Special high-tech gas mixtures such as hydrogen-nitrogen are used to minimize decomplression sickness.
d. Diving with compressed air or other gas mixtures carried by the diver (scuba diving):
There are two types of diving equipment: open and closed circuit devices. In open devices, the exhaled air is released completely through the regulator in the water. This is the technical variant used by most scuba divers. In closed loop systems, the exhaled air is inhaled again after carbon dioxide is removed and oxygen is supplied. These devices were widely used even before the scuba diving device was introduced. This type of diving is typical of military divers, who used these devices so they won’t be recognized in the water due to the rising air bubbles from exhaling. Even with this diving equipment, the divers are at risk of having decompression sickness if they surface without correct decompression.
In general, it is possible to classify the different scuba diving techniques according to the technology used to dive. This classification is therefore basically oriented in a more or less chronological way, according to the advent of different technologies allowing people to evolve underwater:
– Freediving or snorkelling, practiced by freedivers, underwater hunters and underwater hikers.
Depending on the type of suit used:
– Helmet scuba diving
– Rigid scuba diving
– Scuba diving
Depending on the type of breathing circuit used:
– Hookah diving (open circuit)
– Air or mixed diving (open circuit)
– Diving with a rebreather (closed circuit)
Depending on the gas breathed:
– Compressed air diving
– Tech” or “Teak” diving where the diver breathes a mixture of gases
This article focuses on scuba diving, which is the most common scuba diving in the world since the 1950s and 1960s. Open-circuit gases are expelled from the breathing circuit each time the diver exhales (bubble production).
Closed-loop gases remain in the diver’s equipment and are “recycled” with each exhalation. The device eliminates some components of the expired gas, and introduces others, to produce respirable gas again in the same supply circuit (little or no bubble production).