diving

diving. A simple definition of diving is that it is the art of going underwater and coming to the surface again. In antiquity it offered communities living at subsistence level a means of harvesting rivers and the shallower margins of the sea. A brief glimpse of what was involved in this was provided in 8th-century Japanese chronicles which detailed the activities of the Ama, sea folk, originally both male and female, who lived by making salt, catching fish, gathering seaweeds, shellfish, and sea slugs. Sometimes they worked from the surface, but often they had to dive quite deep while holding their breath.

The epic of Gilgamesh (c.2800–2500 bc), a Sumerian king from the head of the Persian Gulf, relates how he made a voyage beyond the waters of death in search of a magical plant capable of granting immortality. Learning that it only grew on the seabed he attached stone weights to his feet so that he could descend and make his search, cutting them loose once he had reached the bottom. This is a technique that may have been associated with pearl fishing, as in the ancient world the island of Dilmun, modern day Bahrain in the Persian Gulf, traded in pearls with southern India.

Some divers in the distant past appear to have mastered the technique that modern divers call ‘ear clearing’. This is the equalization of air and water pressures across the eardrums during a descent to avoid pain and possible physical damage, a mild form of which will be recognized by anyone who has been in a descending aircraft. Those who did master this technique could then dive relatively deep, repeatedly, and without problem. One of them must have been the ancient Greek sea god Glaucus, who was considered a good fisherman and diver before he drowned in a storm, and became immortal in legend.

Early Diving Equipment.

The main limitation of what is now called free-diving, or simply holding your breath, is that it allowed, and still allows, a maximum of around two minutes underwater. It was, however, the only way of diving available until the early first millennium ad when equipment began to be invented that allowed the diver to stay much longer beneath the surface. The earliest example of such equipment is attributed to Aristotle and appeared in a work called Problems. This described an upturned cauldron containing air being carefully lowered to the bottom, so that the diver could enter it if necessary and make use of the air it contained.

Other influences on the later development of diving equipment may well have come from stories which began to circulate early in the 12th century ad, for example Alexander the Great's supposed descent in a glass vessel, and a contemporary German poem describing how Salman and Morolff descended in a boat with an air pipe attached. Then in the 15th century diving helmets began to be mentioned in treatises written by German and Italian military engineers, which were intended to help recover goods and guns lost when merchants or armies crossed rivers. They probably worked, albeit for a limited time and in the shallows, though some danger would have been attached to their use. Some even had an air pipe attached, and all represented attempts to make the diver mobile and able to work more efficiently than free-diving divers.

The beginning of the 16th century saw the introduction of ‘larger-volume diving bells’, as they were called, which potentially offered more time underwater. The first such bell on record was ‘mobile’, as it could be carried around by the diver. Undoubtedly based on practical experience, it was designed by a Maestro Lorena and used by Franco di Marchi (1539) for a dive on the remains of one of the Emperor Caligula's pleasure craft in Lake Nemi, near Rome. It became noticeably heavier when the diver was on the bottom, which he found impeded his movement. We now know that this was due to the bell's air volume being progressively compressed by water pressure during the descent, though an explanation for this phenomenon had to wait until Robert Boyle (1627–91) finally explained the mathematical relationship between (water) pressure and gas volumes. His work not only left us what we now call Boyle's law, but a better understanding of buoyancy and how better to control it.

While there is some evidence of mobile bells being used successfully in the first half of the 17th century, Aristotelian ideas still held sway and consequently most bells followed the upturned cauldron design described in Problems. They had to be heavy enough to sink easily, but this caused problems for their support ships which often had difficulties lowering them onto a worksite, then lifting them again using an ordinary ship's tackle. A further difficulty concerning mobility was that the bell divers could only work for as far as they could reach out under the bell rim, and this often meant lifting and moving the bell over short dis-tances.

This is probably why, at the end of the 17th century and in the early 18th century, the first attempts were made to make more lightweight individual gear. Typically, this comprised a ‘pressure-proof’ body armour, from which the arms and/or legs protruded within a leather suit. There were a number of accidents with this equipment, but from 1720 John Lethbridge, then Jacob Rowe, both of them employed in salvage, used pressure-proof wooden ‘barrels’ from which only their arms protruded. This not only worked successfully in depths up to 20 metres (66 ft) but gave them a degree of mobility while working on a site. Lethbridge and Rowe survived on the air they took down with them inside their ‘barrel’, but from the mid-17th century there were several attempts to supply air continuously with an air pipe and bellows. The civil engineer John Smeaton is the first on record to make this work successfully when in 1779 he used a pump on a very small diving bell to repair, in very shallow water, the foundations of a bridge at Hexham in Northumberland.

More Advanced Diving Bells and Diving Suits.

As a result of the Industrial Revolution, the early 19th century saw an increased use of diving bells fabricated in cast iron, which were heavy enough to require dedicated handling systems. Some were even mounted on ships, with the bell being launched through a central ‘moon pool’, or hatch. Air pump design and efficiency also began to improve, allowing bells to work at greater depth, stay down much longer, and so find an application in the building of a number of harbour breakwaters. The civil engineer John Rennie first became involved in these construction projects early in the century and he soon improved work safety and efficiency. He first placed a one-way air inlet valve where the air pipe entered the bell, and then designed a gantry that allowed the bell and its pump to be moved around and located over any position on a work site.

The beginning of the 19th century also saw more reliable air pumps being used to supply ‘flexible’ diving dresses which, unlike the 18th-century armoured equipment and barrels, allowed divers to walk around freely, use their hands, and potentially become much more cost-effective and productive when tackling intricate jobs. In 1823 Charles Deane patented a ‘smoke’ helmet design, for use in firefighting. It failed to make an impact but in September 1830 his brother John adapted it to inspect a pier of Blackfriars Bridge over London's River Thames in what was to be the first recorded commercial use of a flexible diving dress. The helmet was attached to a short canvas jacket, pulled on over a full-length waterproof dress made of the newly invented Macintosh material. Later termed an ‘open’ dress design, because surplus air was free to escape under the canvas jacket's lower edge, experience soon showed that the helmet could easily displace and drown the diver. To remedy this, an American, John Norcross, introduced a completely ‘closed’ dress design in 1834 that in theory allowed a diver to turn a somersault underwater. To stop the ‘closed’ dress from ballooning, due to excess air being trapped, Norcross used an air-escape pipe hanging down from his helmet. In 1835 Mr Fraser proposed a reliable mechanical air-escape valve attached to the helmet, after which a German, Augustus Siebe (1788–1872), perfected the ‘closed dress’ design between 1839 and 1844, during successful salvage work on the warship Royal George. The resultant familiar copper helmet became standard equipment which remains in use today in many parts of the world.

Early SCUBA Equipment.

In 1664, Robert Boyle's one-time assistant Robert Hooke had both proposed and supervised the development and first practical use of what we now call self-contained equipment, known by the acronym SCUBA (self-contained underwater breathing apparatus), in which air was fed to the diver from inverted lead boxes. Intended for use by a diver walking out to work from a bell, as a way of getting around the problems of moving heavy bells around, it laid the foundations for lightweight equipment that allowed the diver to carry around his own air supply and so remain independent of the surface. In the early 19th century it was realized that the globes and cylinders designed to hold combustible gases under (relatively low) pressure for industrial and domestic lighting use could also be used to hold air for self-contained diving. Similarly, it was the valves required to control the pressure of coal gas supplies in towns that, in 1826, led the Frenchman Jean Jérémie Pouilliot to propose the first regulator, intended to provide air from a cylinder to the diver on his demand (i.e. only when he inhaled, which cut down air wastage) and at ambient pressure according to his depth. The best-known 19th-century self-contained equipment, based on a mechanical regulator, was later designed by Rouquayrol and Denayrouze (1864) and fictionally used by Captain Nemo in Jules Verne's classic Twenty Thousand Leagues under the Sea (1868).

Advances in Knowledge and Equipment.

All this self-contained equipment was ‘open circuit’, where the diver exhaled into the water. This was not very efficient, as the diver only ever used a small part of the 20% oxygen available in a breath of air. Around the middle of the 19th century a remedy for this was found with ‘closed circuit’ or ‘re-breather’ equipment where the diver breathed pure oxygen and his exhalations then passed through a chemical (often caustic potash) which removed the dangerous carbon dioxide. The volume was then ‘made up’, as divers now say, by introducing a small amount of oxygen so that the gas could be safely re-breathed. The viability of this method was shown by Henry Fleuss's successful gear which was patented in 1879.

Improvements in steel manufacture led, from the beginning of the 20th century, to the introduction of cylinders which worked at higher pressures (typically, 100–120 bars) and held more gas, and these were to aid the further development of SCUBA diving. The same period also saw an increased use of submarines by various navies, some of which were soon involved in accidents. This, along with a requirement for practice torpedo recovery, led to a greater demand for safe deep-diving practices, and in 1905 the British Admiralty convened a committee to review the requirements for these. An important outcome was that its physiological member, Professor J. B. S. Haldane, developed tables to combat decompression sickness. These were soon in use by the Royal Navy and other navies and, while there are more modern decompression theories, the procedures the tables laid out are still followed, although in amateur diving wrist-mounted decompression computers have come into widespread use.

Another important advance had by this time already occurred when, in 1878, the French physiologist Paul Bert recognized that oxygen became toxic to breathe above a certain pressure. This led, just prior to the First World War (1914–18), to the development of safer mixed-gas closed-circuit equipment (typically using oxygen-nitrogen mixtures) in both Britain and Germany. However, as the Royal Navy initially used pure oxygen submarine-escape equipment during the Second World War (1939–45), there were some deaths in training before mixed gases, along with much improved equipment, were adopted.

The Aqualung.

In 1918, a Japanese inventor named Ogushi patented ‘The Peerless Respirator’. Reportedly used in the Pacific pearling industry, the diver wore a full-face mask, which covered eyes, nose, and mouth, into which air flowed from a back-mounted cylinder when he compressed a spring-loaded valve held in his mouth. In 1924 Commandant Yves Le Prieur introduced a similar mask into which air free-flowed by way of a reduction valve from a cylinder mounted on the diver's chest. To save air, in 1933 he made the reduction valve diver-adjustable, though, being free flow, dive times still remained very short. Le Prieur is important to the history of recreational diving because, with Jean Painlevé, he started a club in Paris in 1935 which introduced any number of young and old alike to the pleasures of diving.

The mobility of the self-contained diver was assured when, in 1933, Commandant Corlieu introduced the modern foot-fin, and in 1938 the modern spectacle style of face mask started to be marketed by Alexandre Kramarenko of Nice. The same year Maxime Forjot patented the snorkel tube, though it is said that one had been in use for some time by Steve Butler, ‘the English librarian of Juan-les-Pins’. Then in July 1943 an oft forgotten pioneer, Georges Commeinhes, used his own design of demand regulator to reach a depth of 53 metres (175 ft) off Marseille. The same year Frédéric Dumas descended to 64 metres (210 ft) to set a new depth record, using an early version of the ‘twin hose’ regulator.

This regulator, marketed from the mid-1940s under the name of ‘Aqualung’, was the invention of two more Frenchmen, Commandant Jacques-Yves Cousteau and Émile Gagnan. On the diver's demand this delivered air from a back-mounted cylinder in two stages of pressure reduction. The modern ‘single-hose’ regulator first appeared in the 1950s, and it is still in use today. This combined in one unit, which was held in the diver's mouth, the diaphragm that sensed water pressure differentials and the exhaust valve. Over the years its design has seen further improvement, and today it is used in conjunction with cylinders capable of holding air or gas mixtures at pressures up to 300 bar. This gives divers much more control over the way they plan their diving, which for amateur sports is diving in depths up to 50 metres (165 ft).

The deeper diving carried out by Cousteau's team from the early 1940s also led to an appreciation of the dangers of nitrogen narcosis, the narcotic effect due to nitrogen in air that increases as a diver descends. Its study in the 1950s led to the use of the less narcotic helium gas in place of nitrogen in gas mixtures. This in turn paved the way for the development of modern deep-diving techniques and to deeper amateur ‘technical diving’, as it is called, which makes use of both ‘open’-and ‘closed’-circuit equipment.

Modern Commercial Diving.

Commercial deep diving is often carried out using ‘saturation’ diving techniques, where the divers live for weeks in a chamber on the surface held at a pressure slightly less than the ambient pressure on the seabed. The chamber connects to a ‘closed’ diving bell, which can be disconnected so that two divers can descend to the seabed to work perhaps a twelve-hour shift, or even more. As the offshore oil and gas industry has moved into much deeper water, underwater maintenance is nowadays often planned around using underwater vehicles, some fitted with tools designed to carry out simple tasks. However, diver intervention with its ‘hands-on’ capability often remains as a back-up. Atmospheric Diving Suits (ADS), which resist pressure at great depths, allow a diver to apply his or her ‘hands-on’ skills.

The HARDSUIT 2000, an ADS developed for the US Navy, allows a diver to descend as deep as 610 metres (2,000 ft) while the suit in which he is enclosed maintains the same pressure regardless of depth. It is equipped with hydraulic rotary joints, which allow the diver to move his arms and legs, and manipulators which allow him to grasp and move objects underwater. The diver is also able to control four thruster modules, two vertical and two horizontal, with which he can manoeuvre the frame in which he stands. However, the limitation of ADS outside military use is that, even in commercial diving, international regulations stipulate that there must always be a ‘stand-by’ diver ready to assist in an emergency. For some applications, then, this requirement reduces the cost effectiveness of ADS units, as it implies that there must always be a second one immediately available.

Bibliography

Davis, R. , Deep Diving and Submarine Operations (5th edn. 1951).
Harris, G. , IRONSUIT: The History of the Atmospheric Diving Suit (1995).
Vallintine, R. , Divers and Diving (1981).

Anyone wishing to dive should first receive training from qualified and experienced instructors working in a recognized diving school.

British Sub-Aqua Club www.bsac.org

PADI www.padi.com/english

Peter Dick