The history of underwater diving begins with freediving as a popular means of gathering and hunting, both for food and other valuable kinds of stuff such as coral and pearls. By classical Roman and Greek times, commercial applications such as marine salvage and sponge diving were installed. Military diving also has a vibrant history, going back at least as far as the Peloponnesian War, with sporting and recreational applications being modern. Technological development in ambient pressure diving began with skandalopetra (stone weights) for a fast descent. In the early 16th and 17th centuries, diving bells became remarkably useful when a renewable provision of air could be presented to the diver at depth and evolved to surface supplied diving helmets – in effect, miniature diving bells encompassing the diver’s head and supplied with compressed air by manually operated pumps – which were developed by adding a waterproof suit to the helmet and in the late 19th century became the standard diving dress.
Limitations in the mobility of the surface-supplied systems supported the evolution of both open and closed circuit scopes in the 20th century, allowing the diver more comprehensive autonomy. During World War II, these also became popular for covert military operations, and post-war for scientific, media diving, search and rescue, technical and recreational diving. The heavy free-flow surface provided copper helmets evolved into lightweight demand helmets, which are more efficient with breathing gas, which is especially important for deeper dives and costly helium-based breathing mixtures, and saturation diving decreased the risks of decompression sickness for long and deep exposures.
An alternative approach was developing armored suit or the “single atmosphere”, which separates the diver from the depth pressure, at the cost of limited dexterity and great mechanical complexity. The technology first became possible in the middle 20th century. Separation of the diver from the background was taken further by developing remotely operated underwater carriers in the late 20th century. The operator controls the ROV from the outside, and underwater vehicles, which dispense with an operator altogether. All of these methods are still in use, and each has a variety of applications where it has improvements over the others. However, diving bells have primarily been relegated to a means of transport for outside supplied divers. In some cases, combinations are instrumental, such as the concurrent use of saturation surface or surface orientated diving equipment provided and work or observation class remotely operated vehicles.
Although decompression sickness’s pathophysiology is not yet completely understood, the decompression method has reached a stage where the risk is relatively low. Most incidences are successfully treated by hyperbaric oxygen therapy and therapeutic recompression. Mixed breathing gases are routinely used to overcome the effects of the hyperbaric conditions on ambient pressure divers.
Humans practiced underwater diving in ancient cultures to gather food and other vital resources such as corals and pearls and later reclaim sunken valuables and help military aid campaigns. Breath-hold diving was the only way available, seldom using reed snorkels in shallow water and stone weights for longer dives.
Underwater diving for commercial reasons may have evolved in Ancient Greece since both Homer and Plato mention the sponge as being used for bathing. The Kalymnos island was the main center of diving for sponges. By using skandalopetra (weights) of as much as 33 lb (15 kilograms ) to speed the fall, breath-holding divers would dive to depths up to 98 ft (30 meters) for as much as four minutes to collect sponges. Sponges were not the only precious harvest to be found on the seafloor; the harvesting of red coral was also very popular. A variety of fish or valuable shells could be harvested in this way, creating a need for divers to gather the sea treasures, including the underwater riches of other seafarers.
The diving bell is one of the oldest kinds of equipment for underwater exploration and work. Aristotle first described its use in the 4th century BC: “…they allow the divers to breathe equally well by letting down a cauldron, for this does not fill with water, but retains the air, for it is forced straight down into the water.” According to Roger Bacon, Alexander the Great traveled the Mediterranean on the authority of Ethicus the astronomer.