20th Century:

• 1900: John P. Holland builds the first successful submarine, Holland (also called A-1).
• 1900: ## Leonard Hill uses a frog model to prove that decompression causes bubbles and that recompression resolves them.
• 1903: Siebe Gorman starts to make a submarine escape set in England; in the years afterwards it was improved, and later was called the Davis Escape Set or Davis Submerged Escape Apparatus.
• 1905 Several sources, including the 1991 US Navy Dive Manual (pg 1-8), state that the MK V Deep Sea Diving Dress was designed by the Bureau of Construction & Repair in 1905, but in reality, the 1905 Navy Handbook shows British Siebe-Gorman helmets in use. Since the earliest know MK V is dated 1916, these sources are probably referring to the earlier MK I, MK II, MK III & MK IV Morse and Schrader helmets.
• 1905: The first rebreather with metering valves to control the supply of oxygen is made.
• 1907: Draeger of Lübeck makes a rebreather called the U-Boot-Retter. = "submarine rescuer".
• 1908: ## John Haldane, Arthur Boycott, and Guybon Damant publishes "The Prevention of Compressed-Air Illness", detailed studies on the cause and symptoms of decompression sickness, and propose a table of decompression stops to avoid the effects.
• 1908: ## The Admiralty Deep Diving Committee adopts the Haldane tables for the Royal Navy, and publish Haldanes diving tables to the general public.
• 1912: ## US Navy adopts the decompression tables published by Haldane, Boycott and Damant. Driven by Chief Gunner George Stillson, the navy sets up a program to test tables and staged decompression based on the work of Haldane.
• 1913 The Navy also begins developing the future MK V, influenced by Schrader and Morse designs.
• 1915 The submarine USS F-4 is salvaged from 304 feet establishing the practical limits for air diving. Three US Navy divers, Crilley, Loughman, and Nielson, reached 304 fsw using the MK V dress.
• 1916 With the addition of a battery-powered telephone, the design of the MK V is finalized – however, several more design improvements are made over the next two years.
• 1916: The Draeger model DM 2 becomes standard equipment of the German Navy.
• 1917 The Bureau of Construction & Repair introduces the MK V helmet and dress, which then becomes the standard for US Navy diving until the introduction of the MK 12 in the late seventies
• 1918: Ohgushi (he was Japanese) patents "Ohgushi's Peerless Respirator". It was a constant-flow diving and industrial open-circuit breathing set. The user breathed through his nose and switched the air on and off with his teeth.
• 1926: Draeger displayed a rescue breathing apparatus that the wearer could swim with. While the previous devices served only for ascending to the surface and were designed also to develop lift so that the wearer arrived at the surface without swimming movements, the diving set had weights, which also made it possible to dive down with it, to search and save after an accident.
• 1937: US Navy publishes its revised diving tables based on the work of O.D. Yarbrough.

Swim-diving starts:

• The 1930s:
  • In France, Guy Gilpatrick starts swim diving with waterproof goggles, derived from swimming goggles (which were originally intended to keep salt water out of the eyes at the surface).
  • Sport spearfishing became common in the Mediterranean, and spearfishers gradually developed the common sport diving mask and fins and snorkel, and Italian sport spearfishers started using oxygen rebreathers. This practice came to the attention of the Italian Navy, which developed its frogman unit Decima Flottiglia MAS using oxygen rebreathers and manned torpedoes, playing a large role in World War II.
• 1933:
  • In France, Louis de Corlieu patents the first swimming swimfins.
  • In San Diego, California, the first sport diving club is started, called the Bottom Scratchers. As far as it is known, it did not use breathing sets; its main aim was spearfishing.
  • Yves Le Prieur invents a constant-flow open-circuit breathing set. It is said that it could allow a 20 minute stay at 7 meters and 15 minutes at 15 meters. It has one cylinder feeding into a circular fullface mask. Its air cylinder was often worn at an angle to get its on/off valve in reach of the diver's hand; this would have caused an awkward skew drag in swimming.
• 1934:
  • In France a sport diving club is started, called the Club des Sous-l'Eau. It did not use breathing sets as far as is known. Its main aim was spearfishing.
  • Otis Barton and William Beebe dive to 3028 feet using a bathysphere.
• 1935: The French Navy adopts the Le Prieur breathing set.
• 1936: On the French Riviera, the first known sport scuba diving club started. It used Le Prieur's breathing sets.
• 1937: The American Diving Equipment and Salvage Company (now known as DESCO) develops a heavy bottom-walking-type diving suit with a self-contained mixed-gas helium and oxygen rebreather.
• 1939: Hans Hass developed from the escape set a type of rebreather with its bag on his back and two breathing tubes but no backpack box. These sets appear much in his movies and books.

The diving regulator reappears:

• 1937: ## US Navy publishes its revised diving tables based on the work of O.D. Yarbrough.
• 1937: Georges Commeinhes developed a two-cylinder open-circuit apparatus with demand regulator. The regulator was a big rectangular box between the cylinders. Some were made, but WWII interrupted development.
• 1939: Georges Commeinhes offers his breathing set to the French Navy, which could not continue developing uses for it because of WWII. In July 1943 he reached 53 meters (about 174 feet) using it off the coast of Marseille. But he died in 1944 in the liberation of Strasbourg in Alsace. His invention was submerged by Cousteau's invention.
  • Christian J. Lambertsen of the United States designed a 'Self-Contained Underwater Oxygen Breathing Apparatus' for the U.S. military. It was a rebreather. It was the first device to be called SCUBA.
• 1941 to 1945: World War II
  • Various nations use frogmen equipped with rebreathers for some of the best known and most spectacular war actions: see Human torpedo.
  • Hans Hass later said that during WWII the German diving gear firm Dräger offered him an open-circuit scuba set with a demand regulator. It may have been a separate invention, or it may have been copied from a captured Commeinhes-type set.
  • 1943: Jacques Cousteau and Emile Gagnan invent and make an open-circuit diving breathing set, using a demand regulator which Gagnan modified from a demand regulator used to let a petrol-driven car run on a big bag of coal-gas carried on its roof during wartime shortages of petrol. Cousteau had his first dives with it. He made two more aqualungs: there were now 3, one each for Cousteau and his first two diving companions Frédéric Dumas and Taillez. His aqualung remained a secret until the south of France was liberated. This type of breathing set was later named the "Aqua-Lung". This word is correctly a tradename that goes with the Cousteau-Gagnan patent, but in Britain it has been commonly used as a generic and spelt "aqualung" since at least the 1950s, including in the BSAC's publications and training manuals, and describing scuba diving as "aqualunging".
  • 1944: In October, Frédéric Dumas reaches 62 meters (about 200 feet) with a Cousteau aqualung.
  • 1945: Cousteau's first aqualung is destroyed by a mis-aimed artillery shell in an Allied landing on the French Riviera: that left two. Afterwards, he had more aqualungs made and gathered more men and taught them to aqualung dive. In Toulon he started an unofficial mine-clearing and wreck-clearing unit. Later this unit was made official. One of the men who he trained was Broussard, who founded the first post-WWII scuba diving club, the Club Alpin Sous-Marin.
  • The public first hears about frogmen.
  • The first known underwater diving club in Britain, "The Amphibians Club", is formed in Aberdeen by Ivor Howitt (who modified an old civilian gas mask) and some friends. They called underwater diving "fathomeering", to distinguish from jumping into water.
• 1946:
  • Cousteau-type aqualungs go on sale in France.
  • Yves Le Prieur invents a new version of his breathing set. Its fullface mask's front plate was loose in its seating and acted as a very big and therefore very sensitive diaphragm for a demand regulator: see Diving regulator#Demand valve.
• 1948: Auguste Piccard sends the first bathyscaphe, FNRS-2, on unmanned dives.
  • Siebe Gorman and/or Heinke start making Cousteau-type aqualungs in England. Captain Trevor Hampton had a dive with one. Siebe Gorman and the Royal Navy expected aqualungs to be used with weighted boots for bottom-walking for light commercial diving: see Aqua-lung#"Tadpoles".
  • Ted Eldred in Australia starts designing the first open-circuit single-hose scuba set known: see Porpoise (make of scuba gear).
• 1948 or 1949: Rene's Sporting Goods shop in California imports aqualungs from France. Hollywood sees them and gets interested.
• 1949: Otis Barton makes record dive to 4,500 feet in his Benthoscope.
• 1950: Cousteau-type aqualungs go on sale (but very expensive) to industry and civilians in Britain. Siebe Gorman made it at Chessington.
  • A British naval diving manual printed soon after this said that the aqualung is to be used for walking on the bottom with a heavy diving suit and weighted boots, and did not mention Cousteau.
  • A report to Cousteau said that only 10 aqualung sets had been sent to the USA because the market there was saturated.
• 1951: The movie "The Frogmen" is released. It is set in the Pacific Ocean in WWII. In its last 20 minutes, it shows USA frogmen, using bulky 3-cylindered aqualungs on a combat mission. This equipment use is anachronistic (in reality they would have used rebreathers), but it shows that aqualungs were available (even if not widely known of) in the USA in 1951.
  • 1951: The US Navy starts to develop wetsuits, but not known to the public.
  • 1951: In December, the first issue of Skin Diver Magazine (USA) appears. The magazine ran until November 2002.
  • Cousteau-type aqualungs go on sale in Canada.
• 1952: Cousteau-type aqualungs go on sale in the USA.
  • Ted Eldred in Australia starts making for public sale the Porpoise (make of scuba gear). This was the world's first commercially available single-hose scuba unit and was the forerunner of most sport SCUBA equipment produced today.

Public interest in scuba diving takes off:

• 1953: The National Geographical Society Magazine publishes an article about Cousteau's underwater archaeology at Grand Congloué island near Marseille, and in French-speaking countries a diving film called Épaves (Shipwrecks) came out. That started a massive public demand for aqualungs and diving gear, and in France and America the diving gear makers started making them as fast as they could. But in Britain Siebe Gorman and Heinke kept aqualungs expensive, and restrictions on exporting currency stopped people from importing them. Many British sport divers used home-made constant-flow breathing sets and ex-armed forces or ex-industrial rebreathers. In the early 1950's, diving regulators made by Siebe Gorman cost £15, which was an average week's salary.
  • After the supply of war-surplus frogman's drysuits ran out, free-swimming diving suits were not readily available to the general public, and as a result many scuba divers dived with their skin bare except for swimming trunks. That is why scuba diving used often to be called skindiving. Others dived in homemade drysuits, or in thick layers of ordinary clothes.
  • After the supply of war-surplus frogman's fins dried up, for a long time fins were not available to the public, and some had to resort to such things as gluing marine ply to plimsoles.
  • Captain Trevor Hampton founds the British Underwater Centre at Dartmouth in Devon in England.
  • Rene's Sporting Goods shop (now owned by Spirotechnique) becomes U.S.Divers, which is now a leading maker of diving equipment.
• 15 October 1953: The BSAC is founded.
• 1954: USS Nautilus, the first nuclear-powered submarine, is launched.
  • The first manned dives occur in the bathyscaphe FNRS-2.
  • First scuba certification course in the USA is offered by the Los Angeles County Department of Parks and Recreation. Program was created by Albert Tillman and Bev Morgan.
• 1955: In Britain, "Practical Mechanics" magazine publishes an item "Making an Aqualung".
• 1955: Louis Malle, a young film maker of 23, and Jacques-Yves Cousteau shoot The Silent World, one of the first films to use underwater cinematography to show the ocean depths in color.
• 1956: Wetsuits become available to the public.
• 1956: ## US Navy publishes tables that allow for repetitive diving.
  • Around this time, some British scuba divers start making homemade diving demand regulators from industrial parts, including Calor Gas regulators. (Since then, Calor Gas regulators have been redesigned, and this conversion is now impossible.)
  • Later, Submarine Products Ltd in Hexham in Northumberland, England designed round the Cousteau-Gagnan patent and made sport diving breathing sets accessibly cheap. This forced Siebe Gorman's and Heinke's prices down and started them selling to the sport diving trade. (Siebe Gorman gave its drysuit the tradename "Frogman".) Because of this better availability of aqualungs, BSAC's policy towards rebreathers became merely "Here be dragons: keep out!" and remained so for a long time. In the USA, some oxygen diving clubs developed down the years. Eventually, the Cousteau-Gagnan patent time-expired and any firm could legally copy it.
• 1956: The Silent World receives an Academy Award for Best Documentary Feature, and the Palme d'Or award at the Cannes Film Festival.
• 1957: The television series Sea Hunt begins. It introduces SCUBA diving to the television audience. It ran until 1961.
• 1958: USS Nautilus completes the first ever voyage under the polar ice to the North Pole and back.
• 1958: The CMAS (World Underwater Federation) is founded in Brussels.
• 1959: NAUI is founded by Albert Tillman and Neal Hess.
• 1960: Jacques Piccard and Lieutenant Don Walsh, USN, descend to the bottom of the Challenger Deep, the deepest known point in the ocean (about 10900m or 35802 feet = 6.78 miles) in the bathyscaphe Trieste: see at this link andthis link
  • USS Triton completed the first ever underwater circumnavigation of the world.
  • In Italy, sport diving oxygen rebreathers continued to be made well into the 1960s.
• 1965: ## Robert D. Workman of the U.S. Navy Experimental Diving Unit (NEDU) publishes an equation for computing decompression requirements suitable for implementing in a dive computer, rather than a pre-computed table.
  • The film version of James Bond in Thunderball (using both sorts of open-circuit scuba) is released and helps to make scuba diving popular.
• 1966: PADI starts.
• 1968: First known rebreather with electronic parts is made: the Electrolung.
• 1971: Scubapro introduces the Stabilization Jacket, now in England commonly called stab jacket, and elsewhere Buoyancy Control (or Compensation) Device (BC or BCD).
• 1972: Scubapro introduces the decompression meter (the first analogic dive computer).
• 1983: The Orca Edge (the first electronic dive computer) is introduced.
• 1983: ## Professor Albert Bühlmann publishes his work extending the equations to adapt to diving at altitude and with complex gas mixes.
• 1985: The wreck of RMS Titanic is found. Air India Flight 182, a Boeing 747 aircraft, is located and salvaged off Cork, Ireland during the first large scale deep water (6,200 feet) air crash investigation.
• 1989: The film The Abyss (including an as-yet-fictional deep-sea liquid-breathing set) helps to make scuba diving popular.
  • The Communist Bloc falls and the Cold War ends (see Fall of Communism and Collapse of the Soviet Union), and with it the risk of future attack by Communist Bloc forces including by their combat divers. After that, the world's armed forces had less reason to requisition rebreather patents submitted by civilians, and sport diving automatic and semi-automatic mixture rebreathers start to appear. See "rebreather history" link below.

• 1997: The film Titanic helps to make underwater trips onboard MIR submersible vehicles popular.
• 1998 August: Dives on RMS Titanic occur using Remotely Operated Vehicle controlled from the surface (Magellan 725). First ever live video broadcast from the sunken White Star liner is made.

• 1999 July: The Liberty Bell 7 Mercury spacecraft is raised from 16,043 feet (4891.15853659 m) of water in the Atlantic Ocean during the deepest commercial search and recovery operation to date.

• 2001 December: The BSAC allows rebreathers to be used in BSAC dives.