HISTORY of U.S. Navy Diving
Rather than trying to put the History of U.S. Navy Diving into words, the following are links and photographs to be utilized as a guide through U.S. Navy Diving. Some photographs are pre-U.S. Navy and are utilized to show some of the history of Deep Sea Diving in general.
Visit www.divingheritage.com for additional diving history information.
Visit the Historical Diving Society for additional diving history information.
VIEW A HISTORY OF DEEP SEA DIVING via 50 Cards with descriptions
A Brief History of Diving
by David Wiklund
From Antiquity to the Present WHAT IS THE EARLY HISTORY OF DIVING? Men and women have practiced breath-hold diving for centuries. Indirect evidence comes from thousand-year-old undersea artifacts found on land (e.g., mother-of-pearl ornaments), and depictions of divers in ancient drawings. In ancient Greece breath-hold divers are known to have hunted for sponges and engaged in military exploits. Of the latter, the story of Scyllis (sometimes spelled Scyllias; about 500 B.C.) is perhaps the most famous. As told by the 5th century B.C. historian Herodotus (and quoted in numerous modern texts). During a naval campaign the Greek Scyllis was taken aboard ship as prisoner by the Persian King Xerxes I. When Scyllis learned that Xerxes was to attack a Greek flotilla, he seized a knife and jumped overboard. The Persians could not find him in the water and presumed he had drowned. Scyllis surfaced at night and made his way among all the ships in Xerxes's fleet, cutting each ship loose from its moorings; he used a hollow reed as snorkel to remain unobserved. Then he swam nine miles (15 kilometers) to rejoin the Greeks off Cape Artemisium. The desire to go under water has probably always existed: to hunt for food, uncover artifacts, repair ships (or sink them!), and perhaps just to observe marine life. Until humans found a way to breathe underwater, however, each dive was necessarily short and frantic. How to stay under water longer? Breathing through a hollow reed allows the body to be submerged, but it must have become apparent right away that reeds more than two feet long do not work well; difficulty inhaling against water pressure effectively limits snorkel length. Breathing from an air-filled bag brought under water was also tried, but it failed due to rebreathing of carbon dioxide. In the 16th century people began to use diving bells supplied with air from the surface, probably the first effective means of staying under water for any length of time. The bell was held stationary a few feet from the surface, its bottom open to water and its top portion containing air compressed by the water pressure. A diver standing upright would have his head in the air. He could leave the bell for a minute or two to collect sponges or explore the bottom, then return for a short while until air in the bell was no longer breathable. In 16th century England and France, full diving suits made of leather were used to depths of 60 feet. Air was pumped down from the surface with the aid of manual pumps. Soon helmets were made of metal to withstand even greater water pressure and divers went deeper. By the 1830s the surface-supplied air helmet was perfected well enough to allow extensive salvage work. Starting in the 19th century, two main avenues of investigation - one scientific, the other technologic - greatly accelerated underwater exploration. Scientific research was advanced by the work of Paul Bert and John Scott Haldane, from France and Scotland, respectively. Their studies helped explain effects of water pressure on the body, and also define safe limits for compressed air diving. At the same time, improvements in technology - compressed air pumps, carbon dioxide scrubbers, regulators, etc., - made it possible for people to stay under water for long periods. WHAT ARE THE DIFFERENT TYPES OF DIVING? There are really four 'mini-histories' in the fascinating story of man's desire to explore beneath the sea; they correspond to four separate methods of diving, of which scuba is but the latest. a) Breath-hold diving (free diving, skin diving). This earliest form of diving is still practiced for both sport and commercial purposes (e.g., ama divers of Japan and Korea, pearl divers of the Tuamoto Archipe-lago). The breath-hold diver's compressible air spaces are squeezed by the increased water pressure throughout the dive. Each dive, limited by the individual's tolerance for breath-hold and the risk of drowning from hypoxia, is usually a minute or less. b) Diving in a heavy-walled vessel. Heavy-walled vessels can maintain their internal atmosphere at or near sea level pressure ('one atmosphere'or 'one atm.'), and so prevent the surrounding water pressure from affecting the occupants. Such vessels include: the bathysphere, an unpowered hollow steel ball lowered from the mother ship by steel cable; the bathyscaphe, a bathysphere with buoyancy control so that cable is not needed for descent and ascent; and the submarine, which can travel great distances in any direction under its own power. All one-atmosphere vessels require a system to both provide fresh air (usually by adding oxygen to the existing air) and get rid of exhaled carbon dioxide (with soda lime, lithium hydroxide, or a similar compound that takes up CO2). A modern extension of the one-atmosphere vessel is the self- contained armored diving suit, flexible yet able to withstand pressures at depth: in effect, the diver becomes almost like a small submarine. With these one-atmosphere suits a diver can work at a depth of several hundred meters for hours. c) Diving with compressed air supplied from the surface. The diver is separated from the supply of fresh air, which is kept on the surface. Air reaches the diver through a long umbilical, which in its simplest form ends in a regulator and mouthpiece carried by the diver. In more sophisticated systems the umbilical leads into a dive suit or some larger enclosed space containing the diver. Devices in this category include caissons (huge spaces supplied with compressed air, employed mainly for bridge and tunnel work), underwater habitats used for saturation diving, diving bells, and rigid-helmet diving suits. In all these devices the diver breathes air at the same pressure as the surrounding water pressure, and so is at risk for decompression problems (bends, air embolism, etc.) if ascent is too fast. Special 'high tech' mixtures, such as hydrogen-oxygen, helium-oxygen and helium-nitrogen-oxygen, are used to dive deeper than possible with compressed air. d) Diving with compressed air or other gas mixture that is carried by the diver (scuba diving). There are two principle types of scuba: open and closed circuit. Open circuit vents all expired air into the water, and is the mode used in recreational diving. Closed circuit systems, in which exhaled air is re-breathed after carbon dioxide is absorbed and oxygen added, were widely used before open circuit became available, particularly by military divers who wished to avoid showing any air bubbles. As with divers using surface-supplied compressed air, scuba divers are at risk for decompression problems if they ascend without proper decompression. Helium-oxygen and other mixtures can be used to go deeper than possible with compressed air. WHAT ARE SOME IMPORTANT EVENTS IN THE HISTORY OF DIVING? The remainder of this chapter is a chronologic recounting of some important events in the four mini-histories of diving, with emphasis on scuba. There are many legends attached to diving history, some based on isolated woodcuts or the storyteller's art. This list includes selected inventions, discoveries and achievements documented and accepted by historians as fact. Following each date is the type of diving to which the described event is most relevant. (Events that advanced knowledge of diving physics and decompression sickness are relevant to all compressed air diving). The four types of diving are: a) Breath-hold diving ("breath-hold") b) Diving in a heavy-walled vessel ("vessel") c) Diving with compressed air or other gas supplied from the surface ("surface air") d) Diving with compressed air or other gas in a container carried by the diver ("scuba") A BRIEF CHRONOLOGY OF DIVING HISTORY 500 B.C. (breath-hold). Scyllis demonstrates practical use of breath-hold diving by performing military exploits for the King of Persia (see above). 1530 (surface air). First diving bell is invented. 1650 (surface air). Von Guericke develops the first effective air pump. With such a pump Robert Boyle is able to undertake experiments in compression and decompression of animals. 1667 (surface air; scuba). Robert Boyle, English physicist and originator of Boyle's law, observes gas bubble in eye of viper that had been compressed and then decompressed. He writes: "I have seen a very apparent bubble moving from side to side in the aqueous humor of the eye of a viper at the time when this animal seemed violently distressed in the receiver from which the air had been exhausted." This is the first recorded observation of decompression sickness or "the bends." 1690 (surface air). Edmund Halley (of comet fame) patents a diving bell which is connected by a pipe to weighted barrels of air that can be replenished from the surface. Both barrel and bell (the latter with men in it) are lowered to depth; dives to over 60 feet for 90 minutes are recorded. Diving bells are thus shown to be practicable devices. 1715 (surface air). Englishman John Lethbridge builds a "diving engine," an underwater oak cylinder that is surface-supplied with compressed air. Inside this device a diver can stay submerged for 30 minutes at 60 feet, while protruding his arms into the water for salvage work. Water is kept out of the suit by means of greased leather cuffs, which seal around the operator's arms. The diving engine is claimed to be used successfully for many years.
Figure 1. Halley's diving bell, late 17th century. Weighted barrels of air replenished the bell's atmosphere. (U.S. Navy Diving Manual) 1776 (vessel).
First authenticated attack by military submarine - American Turtle vs. HMS Eagle, New York harbor. 1788 (surface air). American John Smeaton refines diving bell; incorporates an efficient hand- operated pump to supply fresh compressed air and a non-return valve to keep air from going back up the hose when pumping stops. In 1790 Smeaton's diving bell is used at Ramsgate Harbor, England, for salvage work. In another 10 years his bell is found in all major harbors. 1823 (surface air). Charles Anthony Deane, an English inventor, patents a "smoke helmet" for fighting fires. At some point in the next few years it is used for diving as well. The helmet fits over a man's head and is held on with weights; air is supplied from the surface through a hose. In 1828 Charles and his brother John Deane market the helmet with a "diving suit." The suit is not attached to the helmet but only secured with straps; thus the diver cannot bend over without risking drowning. Even so, the apparatus is used successfully in salvage work, including the removal of some canon from the Royal George in 1834-35 (see also 1839). 1825 (scuba). "First workable, full-time SCUBA" is invented by an English-man, William James. It incorporates a cylindrical belt around the diver's trunk that serves as an air reservoir, at 450 psi. (It is unclear if this equipment was ever actually used for diving; see Marx 1990 and Brylske 1994 in the Bibliography). Other inventors about this time are also working on self- contained underwater breathing apparatus. 1837 (surface air). German-born inventor Augustus Siebe, living in England, seals the Deane brothers' diving helmet (see 1823) to a watertight, air-containing rubber suit. The closed diving suit, connected to an air pump on the surface, becomes the first effective standard diving dress, and the prototype of hard-hat rigs still in use today. In his obituary Siebe is described as the father of diving.
Figure 2. Siebe's early diving suit. (U.S. Navy Diving Manual) 1839 (surface air).
Seibe's diving suit is used during salvage of the British warship HMS Royal George. The 108-gun ship sank in 65 feet of water at Spithead anchorage in 1783. The "Siebe Improved Diving Dress" is adopted as the standard diving dress by the Royal Engineers. During this salvage, which continues through 1843, the divers report suffering from "rheumatism and cold," no doubt symptoms (among the first recorded) of decompression sickness. Also of note in this salvage is the first recorded use of the buddy system for diving. 1843 (surface air). As a result of experience gained salvaging the HMS Royal George, the first diving school is set up by the Royal Navy. 1865 (surface air, scuba). Frenchmen Benoit Rouquayrol and Auguste Denayrouse, a mining engineer and naval lieutenant, respectively, patent an apparatus for underwater breathing. It consists of a horizontal steel tank of compressed air (about 250-350 psi) on a diver's back, connected through a valve arrangement to a mouth-piece. Patented as the "Aerophore," the device delivers air only when the diver inhales, via a membrane that is sensitive to outside water pressure: in effect, the first demand regulator for underwater use. With this apparatus the diver is tethered to the surface by a hose that pumps fresh air into the low pressure tank, but he is able to disconnect the tether and dive with just the tank on his back for a few minutes. The aerophore is a forerunner of modern scuba equipment. The apparatus is used by the French and other navies for several years, and also appears prominently in Jules Verne's 1870 novel, '20,000 Leagues Under The Sea ' 1873 (surface air). Dr. Andrew H. Smith presents his formal report as Surgeon to the New York Bridge Company, builders of the Brooklyn Bridge, about workers who suffered the bends after leaving the pressurized caisson. (The bends was a common problem among caisson workers. The condition also afflicted chief engineer Washington Roebling; he developed a severe, non-fatal case of decompression sickness, permanently impairing his health). By the time of Smith's report, which recommends chamber recompression for future projects, all Brooklyn Bridge caisson work is completed. Smith's report makes no mention of the true cause of decompression sickness: nitrogen bubbles. 1876 (scuba). An English merchant seaman, Henry A. Fleuss, develops the first workable, self- contained diving rig that uses compressed oxygen (rather than compressed air). In this prototype of closed circuit scuba, which is the forerunner of modern closed circuit scuba units used by military divers, carbon dioxide is absorbed by rope soaked in caustic potash, so that exhaled air can be re-breathed (no bubbles enter the water). Although depths are limited (pure oxygen is toxic below about 25 feet of sea water, a fact not known at the time), the apparatus allows for relatively long bottom times, up to three hours. In 1880 Fleuss's apparatus is used by the famous English diver Alexander Lambert to enter a flooded tunnel and seal a hatchway door; the hatchway is 60 feet down and 1000 feet back into the tunnel.
Figure 3. Aerophore patented in 1865 by BenoitŒt Rouquayrol and Auguste Denayrouse. (Courtesy Historical Diving Society) 1878.
Frenchman Paul Bert publishes La Pression Barometrique, a 1000-page work containing his physiologic studies of pressure changes. He shows that decompression sickness is due to formation of nitrogen gas bubbles, and suggests gradual ascent as one way to prevent the problem. He also shows that pain can be relieved by recompression. Bert provides the link between Boyle's 17th century observation of decompression sickness in a viper and the symptoms of compressed air workers first recorded in the 19th century. 1908 (surface air; scuba). In 1906 the British Government asks John Scott Haldane, an eminent Scottish physiologist, to do research in the prevention of decompression sickness. Two years later Haldane, Arthur E. Boycott and Guybon C. Damant, publish their landmark paper on decompression sickness (from hyperbaric experiments done on goats). "The Prevention of Compressed-Air Illness" lays the groundwork for staged decompression. Tables based on this work are soon adopted by the British Royal Navy and later the United States Navy, and save many divers from the bends. (See Chapter 9) 1912 (surface air; scuba). The U.S. Navy tests tables published by Boycott, Damant and Haldane. 1917 (surface air). The U.S. Bureau of Construction & Repair first introduces the Mark V Diving Helmet. When attached to a deep sea dress and umbilical, the Mark V becomes the underwater work horse for decades to come. It is used for "practically all salvage work undertaken during World War II...the MK V Diving Helmet becomes the standard U.S. Navy Diving equipment until succeeded by the MK12 in 1980." (U.S. Navy Diving Manual). "So sound was its design that very few modifications were ever incorporated, and recent models vary only slightly from the 1917 version." (Leaney 1993) 1920s (surface air; scuba). Research is begun in United States into the use of helium-oxygen mixtures for deep dives. To the beginning of World War II, the U.S. maintains a monopoly on helium. 1924 (surface air; scuba). First helium-oxygen experimental dives are conducted by U.S. Navy and Bureau of Mines. 1930 (vessel). William Beebe, a diving pioneer and "oceanographic naturalist" descends 1426 feet in a round, 4'9" bathysphere; it is attached to a barge by a 7/8" non-twisting steel cable to the mother ship. Of this dive Beebe later writes: ...There came to me at that instant [1426 feet down] a tremendous wave of emotion, a real appreciation of what was momentarily almost superhuman, cosmic, of the whole situation; our barge slowly rolling high overhead in the blazing sunlight, like the merest chip in the midst of the ocean, the long cobweb of cable leading down through the spectrum to our lonely sphere, where, sealed tight, two conscious human beings sat and peered into the abysmal darkness as we dangled in mid-water, isolated as a lost planet in outermost space. 1930s (breath-hold). Guy Gilpatric, an American ex-aviator living in southern France, pioneers use of rubber goggles with glass lenses for skin diving. By the mid-1930s, face masks, fins, and snorkels are in common use. Fins are patented by a Frenchman, Louis de Corlieu, in 1933 (called "Swimming Propellers") and later popularized world-wide by an American entrepreneur, Owen Churchill (see 1940). The modern mask (covering eyes and nose, as opposed to simple eye goggles), evolves from the ideas of various people, including the Russian Alec Kramarenko, and the Frenchmen Yves Le Prieur and Maxime Forjot. In 1934 Gilpatric writes of his Mediterranean exploits for The Saturday Evening Post, and in 1938 publishes The Compleat Goggler, the first book on amateur diving and hunting. Among the book's readers: a French naval lieutenant named Jacques Cousteau. 1933 (breath-hold). First sport divers club is started in California, called the Bottom Scratchers; a year later an amateur diving group, Club des Sous-l'Eau, is founded in Paris. A primary purpose of these and similar clubs is underwater spear fishing. 1933 (scuba). French navy captain Yves Le Prieur modifies the Rouquayrol-Denayrouse invention by combining a specially designed demand valve with a high pressure air tank (1500 psi) to give the diver complete freedom from restricting hoses and lines. The apparatus contains no regulator; the diver receives a breath of fresh air by opening a tap, while exhaled air escapes into the water under the edge of the diver's mask. (In the late 1930s Cousteau used this apparatus but, as he wrote in The Silent World, "the continuous discharge of air allowed only short submersions.") In 1935 Le Prieur's SCUBA is adopted by the French navy. 1934 (vessel). On August 15 William Beebe and Otis Barton descend 3028 feet in a bathysphere near Bermuda. This dive sets a depth record that remains unbroken for 14 years. 1936 (scuba). Le Prieur founds the world's first SCUBA diving club, called the "Club of Divers and Underwater Life." 1938 (surface air; scuba). Edgar End and Max Nohl make the first intentional saturation dive, spending 27 hours at a depth of 101 feet in a Milwaukee hospital hyperbaric chamber. Decompression takes five hours and one of the divers (Nohl) suffers the bends. 1939 (vessel). The first completely successful rescue of submarine-trapped men is carried out. On May 23 the USS Squalus, a new 310-foot submarine, sinks in 243 feet of water during a checkout dive in the North Atlantic. Twenty-six of the crew die instantly in the flooded aft compartments. The forward, unflooded area holds 33 men (including the captain) with enough air and water to last several days. Within hours the largest submarine rescue in history is underway. By midnight of May 25 all 33 men are rescued by a new diving bell, the McCann-Erickson Rescue Chamber. The chamber fits over an escape hatch on the submarine; when the chamber and submarine hatches are opened the men enter the bell under one atmosphere of pressure. Four separate trips are used to rescue the men. The submarine is later salvaged and renovated, and enters World War II duty as the USS Sailfish.
Figure 4. Vertical cross section of the McCann-Erickson Rescue Chamber. (Courtesy U.S. Navy Diving Manual.) 1940.
First year of production of Owen Churchill's swim fins. Initially, only 946 pairs are sold, but in later years production increases substantially, and tens of thousands are sold to the Allied forces. 1941-1944 (scuba). During World War II Italian divers, working out of midget submarines, use closed circuit scuba equipment to place explosives under British naval and merchant marine ships. Later in the war the British adopt this technology to sink German battleship Tirpitz. 1942-43 (scuba). Jacques-Yves Cousteau (a French naval lieutenant) and Emile Gagnan (an engineer for Air Liquide, a Parisian natural gas company) work together to redesign a car regulator that will automatically provide compressed air to a diver on his slightest intake of breath. (Prior to this date, all self-contained apparatus still in use supplied air continuously, or had to be manually turned on and off. For unclear reasons, the 19th century demand regulator of Rouquayrol-Denayrouse had long been abandoned.) Cousteau and Gagnan attach their new demand valve regulator to hoses, a mouthpiece and a pair of compressed air tanks. In January 1943 Cousteau tests the unit in the cold Marne River outside Paris. After a modification (placing the intake and exhaust valves at the same level), they patent the Aqua Lung... The Gagnan-Cousteau regulator fundamentally altered diving. Its simple design and solid construction provided a reliable and low-cost unit for sport diving. Air Liquide put the equipment into commercial production, but it couldn't keep up with the demand. Competitors tried to capture the growing market by producing imitations or making slight adjustments... The devices revolutionized man's perception of the planet. Not unlike the Portuguese, Spanish, and Chinese explorers of the fifteenth century who doubled their knowledge of the size of the world, Cousteau and Gagnan helped open a vast portion of the globe to human exploration. They offered the opportunity for extensive undersea investigation to enthusiastic scientists, engineers, and sportsmen. Summer and fall 1943 (scuba). Cousteau and two close friends, Frederic Dumas and Philippe Tailliez, make over five hundred dives with the aqualung, gradually increasing the depths to which they plunge. They have developed the first workable, open-circuit demand-type scuba apparatus. In October Dumas, in a carefully planned dive, descends to 210 feet in the Mediterranean Sea and experiences l'ivresse des grandes profondeurs - rapture of the great depths. 1946 (scuba). Cousteau's Aqua Lung is marketed commercially in France. (It is marketed in Great Britain in 1950, Canada in 1951 and the USA in 1952). 1947 (scuba). In August, Dumas makes a record dive with the Aqua Lung to 307 feet in the Mediterranean Sea. 1948 (vessel). Otis Barton descends in a modified bathysphere to a depth of 4500 feet, off the coast of California. 1950 (scuba). Despite the technical success of the aqua lung, it has yet to catch on in the U.S. So far only 10 aqua lung units have been shipped to the U.S. because, the distributor tells Cousteau, "the market is saturated." 1951 (breath-hold; scuba). The first issue of Skin Diver Magazine appears in December. 1950s (breath-hold; scuba). The sport of diving gradually changes from breath-hold to mainly scuba. Dive stores open up around the U.S. 1953 (scuba). The Silent World is published. Written in English by Jacques Cousteau, with the assistance of Fr‚d‚ric Dumas, the book chronicles the development and early testing of the Cousteau-Gagnan Aqua Lung. 1950s (vessel). Famed Swiss balloonist August Picard turns his attention to the deep sea. With son Jacques, he pioneers a new type of vessel called the bathyscaphe (deep boat). The bathyscaphe is completely self-contained (not tethered to the surface), and designed to go deeper than any bathysphere. On February 15, 1954, off the coast of French West Africa, a bathyscaphe containing Georges S. Houot and Pierre-Henri Willm exceeds Barton's 1948 diving record, reaching a depth of 13,287 feet. 1957 (scuba). First segment of Sea Hunt airs on television, starring Lloyd Bridges as Mike Hunt, underwater adventurer. The series inspires thousands of people to take up scuba diving. 1959 (scuba). YMCA begins the first nationally organized course for scuba certification. 1960 (vessel). On January 23, Jacques Picard and Navy lieutenant Don Walsh descend to 35,820 feet (10,916 meters, 6.78 miles) in the August Picard-designed, Swiss-built, US Navy-owned bathyscaphe Trieste. This dive takes place in the Pacific Ocean's Mariana Trench, 250 miles southwest of Guam, one of the deepest parts of the world ocean. Water pressure at this depth is 16,883 psi, temperature 37.4°F. Picard observes what he later calls "a flatfish at the very nadir of the earth" but no specimens can be collected. Trieste leaves the surface at 8:22 a.m., reaches maximum depth at 1:10 p.m. and surfaces at 4:30 p.m. No one will ever go deeper (unless, of course, oceanographers discover a deeper spot than the Mariana trench). 1960s (scuba). As accident rates for scuba divers climb, the first national training agencies are formed to train and certify divers; NAUI is formed in 1960, PADI in 1966. 1962 (surface air; scuba). Beginning in 1962 several experiments are conducted whereby people live in underwater habitats, leaving the habitat for exploration (using scuba equipment) and returning for sleeping, eating and relaxing. The habitats are supplied by compressed air from the surface. The first such experiment, Conshelf (Continental Shelf) One, takes place in September 1962. Under the watchful eye of Jacques Cousteau and his team, Albert Falco and Claude Wesley spend seven days under 33 feet of water near Marseilles, in a habitat they name Diogenes. Diogenes was an enormous Aqua-lung into which Falco and Wesley retreated for warmth and food, sleep and hygiene. It was like the air bubble that a water spider takes down to sustain itself in its activities beneath the surface. For our men, the five daily hours outside were more important than the nineteen hours within. (Cousteau 1963) 1963-1965 (surface air; scuba). In 1963, eight divers live in Conshelf Two under the Red Sea for a month. Other habitats of this period: Sealab I (1964); Sealab II (1965); and Conshelf Three (1965), in which former astronaut Scott Carpenter and other divers spend a month at 60 meters off the coast of southern France. 1967 (scuba). PADI, Professional Association of Diving Instructors, trains 3226 divers in its first year of operation. 1968 (scuba). On October 14 John J. Gruener and R. Neal Watson dive to 437 feet breathing compressed air, off coast of Grand Bahama Island. This record is not broken until 1990 (see Diving Odds N' Ends). 1970s (scuba). Important advances relating to scuba safety that began in the 1960s become widely implemented in the 1970s, including: adoption of certification cards to indicate a minimum level of training and as a requirement for tank refills rental of scuba equipment; change from J-valve reserve systems to non-reserve K valves and adoption of submersible pressure gauges; adoption of the buoyancy compensator and single hose regulators as essential pieces of diving equipment (replacing the dual hose, non-BC equipment initially in widespread use). 1980 (scuba). Divers Alert Network is founded at Duke University as a non-profit organization to promote safe diving. 1981 (scuba). Record 2250 foot-dive is made in a Duke Medical Center chamber. Stephen Porter, Len Whitlock and Erik Kramer live in the eight-foot- diameter spherical chamber for 43 days, breathing a mixture of nitrogen, oxygen and helium. They beat their own previous record set in 1980. 1983 (scuba). The first commercially available dive computer, the Orca Edge, is introduced. In the next decade many manufacturers market dive computers, and they become common equipment among recreational divers. 1985 (vessel). U.S.-French team headed by Woods Hole researcher Robert Ballard, using a remote controlled camera attached to the mother ship, finds the wreck of the Titanic. The ship sits broken into two sections at 12,500 feet depth, some 400 miles northeast of New York. On April 15, 1912, five days into its maiden voyage, Titanic hit an iceberg and sank in less than three hours. At the time she was the largest ship in the world. A total of 1522 passengers and crew died. Since 1985 both the U.S. and France have revisited the site, and the French have recovered artifacts from the ship. 1993 (scuba). The 50th anniversary of the invention of modern scuba diving is celebrated around the world. PADI, the largest of the national training agencies, certifies 515,000 new divers worldwide. 1990s (scuba). An estimated 500,000 new scuba divers are certified yearly in the U.S., new scuba magazines form, dive computers proliferate, new liveaboards ply the waters and scuba travel is transformed into a big business. In North America alone recreational diving becomes a multi- billion dollar industry. At the same time there is expansion of "technical diving" Ä diving by non-professionals who use advanced technology, including mixed gases, full face masks, underwater voice communication, propulsion systems, etc.