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A SEAL climbs aboard a SDV before launching from the back of the submarine USS Philadelphia.

A frogman is someone who is trained in scuba diving or swimming underwater in a tactical capacity which includes combat. Such personnel are also known by the more formal names of combat diver, or combatant diver, or combat swimmer. The word frogman arose around 1940 from the appearance of a diver in shiny drysuit and large fins.

Combat swimming is often used to mean combat diving. Such actions are a historical form of "frogman" activity and an important feature of naval special operations.

The term frogman is occasionally used to refer to a civilian scuba diver. Some sport diving clubs include the word Frogmen in their names. The preferred term by scuba users is diver, but the frogman epithet persists in informal usage by non-divers, especially in the media and often referring to professional scuba divers such as in a police diving role.

In the U.S. military and intelligence community, divers trained in scuba or CCUBA who deploy for tactical assault missions are called "combat divers". This term is used to refer to the Navy SEALs, operatives of the CIA's Special Activities Division, elements of Marine Recon, Army Ranger Regimental Reconnaissance Company members, Army Special Forces divers, Air Force Pararescue, Air Force Combat Controllers, United States Naval Search and Rescue Swimmers, United States Air Force Special Operations Weather Technicians, and the Navy Explosive Ordnance Disposal (EOD) units. In Britain, police divers have often been called "police frogmen". Some countries' tactical diver organizations include a translation of the word frogman in their official names, e.g., Denmark's Frømandskorpset and Norway's Froskemanskorpset; others call themselves "combat divers" or similar. Others call themselves by indefinite names such as "special group 13" and "special operations unit".

Many nations and some irregular armed groups deploy or have deployed combat frogmen.

Scope of operations

Combat Camera Underwater Photo Team – A US Navy diver during underwater photography training off the coast of Guantanamo Bay, Cuba.

Tactical diving is a branch of professional diving carried out by armed forces and tactical units. They may be divided into:

  • Combat/assault divers.
  • Special mission work divers (called Clearance Divers in the British Royal Navy and Royal Australian Navy), who do general work underwater.
  • Work divers who are trained in defusing mines and removing other explosives underwater.

These groups may overlap, and the same men may serve as assault divers and work divers, such as the Australian Clearance Diving Team (RAN).

The range of operations performed by these operatives includes:

  • Amphibious assault: stealthy deployment of land or boarding forces. The vast majority of combat swimmer missions are simply to get "from here to there" and arrive suitably equipped and in sufficient physical condition to fight on arrival. The deployment of tactical forces using the arrival by water to assault land targets, oil platforms, or surface ship targets (as in boardings for seizure of evidence) is a major driver behind the equipping and training of combat swimmers. The purposes are many, but include feint and deception, counter-drug, law enforcement, counter-terrorism, and counter-proliferation missions.
  • Sabotage: This includes putting limpet mines on ships.
  • Clandestine surveying: Surveying a beach before a troop landing, or other forms of unauthorized underwater surveying in denied waters. The article "Riding on Proton" by Afonchenko (in Russian) may describe in passing a Soviet Bloc frogman infiltration into South Korean sea.
  • Clandestine underwater work, e.g.:
    • Recovering underwater objects.
    • Clandestine fitting of monitoring devices on submarine communications cables in enemy waters.
  • Investigating unidentified divers, or a sonar echo that may be unidentified divers. Diving sea-police work may be included here. See anti-frogman techniques.
  • Checking ships, boats, structures, and harbors for limpet mines and other sabotage; and ordinary routine maintenance in war conditions. If the inspection divers during this find attacking frogmen laying mines, this category may merge into the previous category.
  • Underwater mine clearance and bomb disposal.

Typically, a frogman with closed circuit oxygen rebreathing equipment will stay within a depth limit of 20 feet (6.1 m) with limited deeper excursions to a maximum of 50 feet (15 m) because of the risk of seizure due to acute oxygen toxicity.[1] Use of nitrox or mixed gas rebreathers can extend this depth range considerably, but this may be beyond the scope of operations, depending on the unit.

Mission descriptions

The U.S. and U.K. forces use these official definitions for mission descriptors:[citation needed]

Keeping out of sight (e.g., underwater) when approaching the target.
Carrying out an action of which the enemy may become aware, but whose perpetrator cannot easily be discovered or apprehended. Covert action often involves military force which cannot be hidden once it has happened. Stealth on approach, and frequently on departure, may be used.
It is intended that the enemy does not find out then or afterward that the action has happened. Installing eavesdropping devices is the best example. Approach, installing the devices, and departure are all to be kept from the knowledge of the enemy. If the operation or its purpose is exposed, then the actor will usually make sure that the action at least remains "covert", or unattributable: e.g., "...the secretary will disavow any knowledge of your actions."

Defending against frogmen

Anti-frogman techniques are security methods developed to protect watercraft, ports and installations, and other sensitive resources both in or nearby vulnerable waterways from potential threats or intrusions by frogmen.


SEAL combat swimmer training

Training armed forces divers, including combat divers, is often harder, longer, and may be more complicated than civilian commercial or recreational scuba diver training.[citation needed] Training typically takes several months full-time,[citation needed] and the trainees must be at full armed forces fitness and discipline at the start. Even higher levels of fitness are generally required to successfully complete the training, and during the course there is often a high elimination rate of trainees who do not make the grade.[citation needed]


Breathing sets

Frogmen's breathing sets on covert operations should have particular features.[opinion][citation needed]

  • Some are needed because they may need to swim fast and far.
  • Some are needed to avoid detection.
  • Sometimes patrol divers may have to be sent down to find or arrest submerged suspect divers. For reasons stated in Anti-frogman techniques#Sending other frogmen against them, underwater fights between divers are much rarer in reality than in fiction, and thus suitability of the frogman's kit for "diver to diver combat" is less important than some other features when designing it; but the point is considered here for completeness.

USA frogmen's rebreathers tended to have the breathing bag on the back before enclosed backpack-box rebreathers became common.

Features needed

US Navy Explosive Ordnance Disposal dive equipment

A frogman's breathing set should:[opinion][citation needed]

  • Be as silent as possible in use.
  • Have a full face diving mask:
    • To let frogmen communicate underwater.
    • Be less easily knocked off underwater.
    • Be much less easily lost if the frogman becomes unconscious underwater.
    • Be securely fastened, see here about full-face diving masks. It should have as little as possible (e.g., an excessively bulky or projecting set/air valve) that can catch on things or that an attacker could easily grasp.
  • Be a dull color to avoid being seen from out of the water. Many are black, but the Russian IDA71's backpack box is mostly dark green. No large bright-colored badges or manufacturer's logos.
  • Contain as little iron or steel as possible, to avoid detection by magnetic sensors. This is also useful when the frogmen have to remove or defuse mines underwater.
  • Be as light and agile as possible, as far as is compatible with an adequate dive duration:
    • Be well streamlined, and as small and light as possible for the dive duration. With a combat diver this may mean removing safety features such as an open-circuit bailout that would add bulk. Long trailing hoses (e.g., regulator hoses) are easily fouled and or pulled at and add to drag. If an underwater fight, or a quick need to escape, develops, agility and lack of cumbersomeness could be vital. This applies to:
      • Streamlining in straight swimming, as he may have to swim fast and far.
      • Streamlining when he rolls over and twists about.
      • The diver's inertia when he must roll over quickly.
      • The risk of snagging on things in dark water, or being taken hold of by. The Russian IDA71 military and naval rebreather is a good example here.
  • Have a long dive duration.
  • The front of the frogman's abdomen should be clear so he can easily climb in and out of small boats or over obstacles, particularly out of the water.
  • Have its breathing bag toughened against stabbing and scratches, or safely inside a hard backpack box.
  • All controls should be where the frogman can easily reach them, and not projecting. Turning the usual type of sport diving scuba's air off or on is easy for an attacker from above but difficult or impossible for the diver himself (and has been known to happen by itself when a diver pushes through thick kelp), unless the cylinder or cylinders are mounted inverted. However, that needs more pipework, and it is easy to bump the valvework on things, including when taking the set off.
  • Have its working parts and breathing tube or tubes should be safe from snagging on things in dark water, and from attack in an underwater fight, including in the risk of being "jumped" from above.
    • Long trailing breathing tubes or regulator hoses may snag on things in dark water and can easily be grasped and pulled.
    • Older Siebe Gorman-type rebreathers (see Siebe Gorman CDBA) had one breathing tube, which was in front of the chest and easier for the frogman to keep track of.

Not open-circuit scuba

As a result, the frogman's breathing set should be[opinion][citation needed] fully closed circuit rebreather, preferably not[opinion][citation needed] semi-closed circuit and certainly not[opinion][citation needed] open-circuit scuba, because:

  • Open-circuit scuba makes large amounts of bubbles, showing where the diver is.
  • Open-circuit scuba makes noise (on exhalation, and regulator valve intake hiss as the diver breathes in) showing underwater listening devices where the diver is.
    • There have been experiments with making released air or gas come out through a diffuser, to break the bubbles up; this may sometimes work with the small amounts of gas that are sometimes released by rebreathers, but open-circuit scuba releases so much gas at every breath that a diffuser large enough to handle it without making breathing difficult would be too bulky and would interfere with streamlining.[2] Holding the breath to avoid making noise at critical moments is not recommended and very risky: see diving hazards and precautions
  • The bulk of an open-circuit set makes the diver heavy and cumbersome in rolling over and changing course or speed.
  • The dive duration of open circuit sets is much shorter than the dive duration of naval rebreathers, in proportion to bulk. However, some "technical diving" rebreathers are very burdened with safety devices such as inflatable flotation and open-circuit bailout. (Some modern rebreathers, such as the Draeger, are lighter.) The rebreathers which are the most compact in proportion to dive duration are oxygen rebreathers, but these are depth limited to about 8 metres (26 ft) because of the oxygen toxicity risk.
  • The common sport open-circuit scuba set is not recommended for a fight against a trained naval or combat diver, because in any sort of underwater combat, a man with a large aqualung has a high rotation-inertia and is very unstreamlined in the twisting and turning involved in fighting and straight swimming, and his maneuvering is slowed critically compared to a man with a light streamlined rebreather with all parts close to his body.

Combat frogmen sometimes use open-circuit scuba sets during training and for operations where being detected or long distance swimming are not significant concerns.

Breathing sets used by frogmen

Russian IDA71

The Russian IDA71 military and naval rebreather is typical of a back-mounted configuration suitable for use by frogmen:

  • The working parts are in a hard, smooth, rounded, metal backpack casing which has little that can snag on things or be easily grasped and pulled at. There is no mass of projecting valvework behind the neck to cause hydrodynamic drag and for an attacker to grasp.
  • The only external control is the oxygen cylinder valve, which is on the right side near the bottom where it can easily be reached, and only sticks out a small distance.
  • The corrugated rubber breathing tubes originate close to where they go over the shoulders. They can be strapped to the shoulder straps so they do not float up into big vulnerable loops behind the shoulders.
  • The holes in the casing let contained water drain to quickly reduce the weight of when exiting the water, and also allow the casing to flood quickly when entering the water, to stabilise buoyancy.
  • The harness may be fitted with a chest mounted bracket for carrying a limpet mine.
  • In closed circuit oxygen mode it is said to last 4 hours on a filling. It can also be used on an automatic depth controlled changeover to nitrox for deep excursions, which uses an external nitrox cylinder with a quick-connector.


Some frogmen use an ordinary diving mask; some use a fullface mask, which is less easily lost underwater. The older type of British frogman's and naval diving mask was full face and had a mouthpiece inside it.[citation needed]

Some frogmen use a mouthpiece and noseclip or a mouth-and-nose (orinasal) breathing mask instead of a diving mask with eye windows, and special contact lenses to correct the vision refraction error caused by the eyeballs being directly submerged.[citation needed] This is to avoid a searchlight or other lights reflecting off the mask window and thus revealing his presence, but it exposes the eyeballs to any pollution, poison, or organisms in the water.

The United States military has adopted Oceanic/Aeris's "Integrated Diver Display Mask". It is a basic "Heads-Up Display" that lets divers monitor depth, bottom time, tank pressures, and related information while leaving their hands free for other tasks.[citation needed]


Another problem with a frogman who may have to come ashore and operate on land is the awkwardness of walking on land in fins, unless he plans to discard his kit and return to base by some other way than by diving, or if the frogmen plan to take and hold a position on land until other troops arrive. Some sport diving fins have the blade angled downwards for more effective swimming, but this makes walking on them more awkward.

The usual solution is for the frogman to take his fins off and carry them, but that takes time and occupies a hand carrying them unless he can clip them into his kit or thread an arm through the fins' straps. Nowadays all fins can be clipped onto a belt without having any disadvantages.

Another type of fin that frogmen could use would have a lockable hinge which on land can be unlocked to let the fin blade hinge up out of the way when walking: for example Flipfins.

The first type of British naval swimming fin had a short blade which was even shorter at the big toe side: this made walking on land easier for such purposes as creeping up on a sentry from behind on land, but reduced swimming speed.

Diving suits

The frogman's diving suit should be a tough scratch-and-cut-resistant drysuit (perhaps reinforced with kevlar), and not a soft foam wetsuit.[citation needed] A wetsuit can be worn under the drysuit as a warm undersuit. In very warm water, a thin tough drysuit can be worn with no undersuit.

For Bomb Disposal Operations, Canadian Naval Divers wear Bomb suits.[Clarification needed]

It should not have obvious bright colored patches, unit badges or the suit's maker's advertising.[citation needed] Diving sea-police types, however, may find that a unit badge is useful.[Clarification needed]

Tools and weapons carried underwater

Weapons that can be carried by a frogman include:

  • Knife: standard weapon.
  • A speargun has been seen advertised in circumstances suggesting its use for combat and not for fishing.
  • Underwater firearms:
  • Standard firearms:
    • Canadian Diemaco C7 and C8 assault rifles
  • Many types of explosives may be used:
  • Other tools include net-cutters.

Operational transport and delivery systems

Frogmen may approach their site of operation and return to base in various ways including:

  • Swimming all the way.
  • Small boats, such as a canoe or sea scooter.
  • Tenders and remotely operated vehicles (ROV).[citation needed] Canadian divers use the Phantom ROV and Yard Diving Tenders (YDT).
  • Being dropped off or picked up by fast rigid-hulled inflatable boats.
  • The Subskimmer and similar.
  • In World War II, Italy and the United Kingdom used manned torpedoes to carry frogmen to their targets. Some nations still keep manned torpedoes.
  • Powerful versions of sport-diving submersibles, modified with longer duration batteries.[citation needed]
  • The Protei 5 and similar diver propulsion vehicles.
  • Midget submarines such as the X-craft, the SEAL Delivery Vehicle or the US Advanced SEAL Delivery System (ASDS) that have an airlock for frogmen to exit and return.
  • Full-sized submarines which frogmen can exit and return to, through an airlock or a torpedo tube. These two methods, need special precautions in buoyancy control. This link (in Russian) describes a risky diving incident from a submerged submarine: the sub was neutrally buoyant at the start, but when the first frogman airlocked, the sub's buoyancy changed causing it to start floating up. In later dives, the ballast was increased to keep the sub on the seabed while frogmen were getting out or in.
  • Some frogmen are trained to parachute to the site of operation. The backpack box of the Russian IDA71 frogman's rebreather has two metal clips to fasten to a parachute harness.[citation needed]


A 1945 British navy frogman with complete gear, including the Davis apparatus, a rebreather originally conceived in 1910 by Robert Davis as an emergency submarine escape set.

A French frogman with chest counterlung loop rebreather with 2 (model "Oxygers", 1957).

In ancient Roman and Greek times, etc., there were instances of men swimming or diving for combat, sometimes using a hollow plant stem or a long bone as a snorkel. Diving with snorkel is mentioned by Aristotle (4th century BC).[3] The earliest descriptions of frogmen in war are found in Thukydides' history of the Peloponnesian War. The first instance was in 425 BC, when the Athenian fleet besieged the Spartans on the small island of Sphacteria. The Spartans managed to get supplies from the mainland by underwater swimmers towing submerged sacks with supplies. In another incident of the same war, in 415 BC, the Athenians used combat divers in the port of Syracuse, Sicily. The Syracuseans had planted vertical wooden poles in the bottom around their port, to prevent the Athenian triremes from entering. The poles were submerged, not visible above the sea level. The Athenians used various means to cut these obstacles, including divers with saws.[4] It is believed that the underwater sawing required snorkels for breathing and diving weights to keep the divers stable.[5]

The Hungarian Chronicon Pictum claims that Henry III's 1052 invasion of Hungary was defeated by a skillful diver who sabotaged Henry's supply fleet. The unexpected sinking of the ships is confirmed by German chronicles.

Italy started World War II with a commando frogman force already trained. Britain, Germany, the United States, and the Soviet Union started commando frogman forces during World War II.

First frogmen

The word frogman appeared first in the stage name The Fearless Frogman of Paul Boyton, who since the 1870s broke records in long distance swimming to demonstrate a new invented rubber immersion suit, which inflated hood had a frog-like shape. As a stunt show hero in that suit he played a military diver (attaching mines to ships etc.) long before such divers existed.

The first modern frogmen were the World War II Italian commando frogmen, of Decima Flottiglia MAS (now "ComSubIn": Comando Raggruppamento Subacquei e Incursori Teseo Tesei) which formed in 1938 and was first in action in 1940. Originally these divers were called "Uomini Gamma" because they were members of the top secret special unit called "Gruppo Gamma", which originated from the kind of Pirelli rubber skin-suit[6] nicknamed muta gamma used by these divers. Later they were nicknamed "Uomini Rana", Italian for "frog men", because of an underwater swimming frog kick style, similar to that of frogs, or because their fins looked like frog's feet.[7]

Italian frogman of "Gruppo Gamma"

This special corps used an early oxygen rebreather scuba set, the Auto Respiratore ad Ossigeno (A.R.O), a development of the Dräger oxygen self-contained breathing apparatus designed for the mining industry and of the Davis Submerged Escape Apparatus made by Siebe, Gorman & Co and by Bergomi,[8] designed for escaping from sunken submarines. This was used from about 1920 for spearfishing by Italian sport divers, modified and adapted by the Italian navy engineers for safe underwater use and built by Pirelli and SALVAS from about 1933, and so became a precursor of the modern diving rebreather.[9][10][11][12]

For this new way of underwater diving, the Italian frogmen trained in La Spezia, Liguria, using the newly available Genoese free diving spearfishing equipment; diving mask, snorkel, swimfins, and rubber dry suit, the first specially made diving watch (the luminescent Panerai), and the new A.R.O. scuba unit.[13] This was a revolutionary alternative way to dive, and the start of the transition from the usual heavy underwater diving equipment of the hard hat divers which had been in general use since the 18th century, to self-contained divers, free of being tethered by an air line and rope connection.

In 1933 Italian companies were already producing underwater oxygen rebreathers, but the first scuba diving set is generally recognised inside the USA as being invented in 1939[citation needed] by Christian Lambertsen, who dubbed it the Lambertsen Amphibious Respirator Unit (LARU).[14] and patented it in 1940.[15] He later renamed it the Self Contained Underwater Breathing Apparatus, which, contracted to SCUBA, eventually became the generic term for both open circuit and rebreather autonomous underwater breathing equipment.

Lambertson demonstrated it to the Office of Strategic Services (OSS) (after already being rejected by the U.S. Navy) in a pool at a hotel in Washington D.C.[16] OSS not only bought into the concept, they hired Dr. Lambertsen to lead the program and build-up the dive element of their maritime unit.[16] The OSS was the predecessor of the Central Intelligence Agency and the maritime element still exists inside their Special Activities Division.[17]

John Spence, an enlisted member of the U.S. Navy, was the first man selected to join the OSS group.[18] In an interview with historian Erick Simmel, Spence claimed that the name "frogman" was coined while he was training in a green waterproof suit, "Someone saw me surfacing one day and yelled out, 'Hey, frogman!' The name stuck for all of us."[18][unreliable source?]

The frogman in popular culture

Derivative word usages

  • Some scuba diving clubs have an entry class called "Tadpoles" for younger children who want to start scuba diving.

Movies and fiction

Frogman-type operations have featured in many comics, books, and movies. Some try to reconstruct real events; others are completely fictional. Some make mistakes as described below. Examples are:

  • The 1951 film The Frogmen, made by Twentieth Century Fox, shows some United States frogman operations against the Japanese in World War II, but with wrong kit (see below).
  • Mike Nelson, lead character in the TV series Sea Hunt, is a former Navy frogman.
  • The 1958 film The Silent Enemy with Laurence Harvey as Lionel "Buster" Crabb, describes his exploits during World War II. It was made following the publicity created by Crabb's mysterious disappearance and likely death during a Cold War incident a year earlier.
  • The James Bond film Thunderball depicts an extended underwater battle, featuring frogmen.
  • Listed at Human torpedo#Movies and fiction.
  • Listed at United States Navy SEALs in fiction.
  • James Bond's modern biography includes serving with the Special Boat Service through the Royal Navy.
  • Simon and Garfunkel's song "Baby Driver" contains the following line: "My daddy was a prominent frogman. My mamma's in the Naval reserve."
  • In the 2013 film adaptation of former Navy SEAL Marcus Luttrell's book Lone Survivor, the men are referred as "frogmen" on multiple occasions.
  • In Jack Neo's film Ah Boys to Men 3: Frogmen, the recruits train to become frogmen.

Errors and misconceptions in public media

Wrong use of the word frogman

A new English translation of the book Twenty Thousand Leagues Under the Sea uses the word frogman uniformly and wrongly to mean a diver in standard diving dress or similar, to translate French scaphandrier.

Supposed ancient scuba divers/frogmen

Ancient Assyrian stone carvings show images which some have supposed to be frogmen with crude breathing sets. However, the "breathing set" was merely a goatskin float used to cross a river, and its "breathing tube" was to inflate it by mouth. See timeline of underwater technology.

Mistakes in fiction

Open circuit scuba

Many comics have depicted combat frogmen and other covert divers using two-cylinder twin-hose open-circuit aqualungs. All real covert frogmen use rebreathers because the stream of bubbles from an open-circuit set would give away the frogman's position.

Many aqualungs have been anachronistically depicted in comics in stories set during World War II, when in reality, at that time period, aqualungs were unknown outside Jacques-Yves Cousteau and his close associates in Toulon in south France. Some aqualungs were smuggled out of occupied France during the war (these may have been Commeinhes aqualungs), but the aqualung for the most part was not a player in combat in World War II.

The movie The Frogmen also made this mistake, using three-cylinder aqualungs, as shown on the DVD cover at this link, and at this link; see also this link. At the time DESCO were making three-cylinder constant flow breathing sets that lacked the demand valve of the aqualung, but they were rarely deployed in the war, and the preferred system in the US armed forces was the rebreather developed by Dr. Christian J. Lambertsen.[19]

After Ian Edward Fraser in 1957 wrote a book, Frogman V.C., about his experiences, whoever designed its dust cover depicted on it a frogman placing a limpet mine on a ship, wearing a breathing set with twin over-the-shoulder corrugated breathing hoses emitting bubbles from behind his neck, presumably drawn after an aqualung.

The film Submarine X-1, made in 1969, loosely based on the real Operation Source, gets British World War II frogman's equipment very wrong and anachronistic. The breathing sets shown were open-circuit and were merely a very fat cylinder across the belly, with a black single-hose second-stage regulator such as was not invented until the 1960s. Also shown were ordinary recreational scuba weight belts and diving half masks with elliptical windows. The frogmen in the real war operation mostly used Sladen suits and an early model of Siebe Gorman rebreather with a backpack weight pouch containing lead balls releasable by pulling a release cord.[citation needed]

Drawing and artwork

There have been thousands of drawings (mostly in comics, some elsewhere) of combat frogmen and other scuba divers with two-cylinder twin-hose aqualungs shown wrongly with one wide breathing tube coming straight out of each cylinder top with no regulator, far more than of twin-hose aqualungs drawn correctly with a regulator,[citation needed] or of combat frogmen with rebreathers. See this image for the correct layout of an early model aqualung.

Another common mistake when drawing a diver standing with a bulky backpack breathing set is to show him standing vertically, whereas in reality he would lean forwards somewhat, as the weight of a backpack breathing set (20 kg or more with big twin air cylinders) pushes his center of gravity backwards. The also happens with a film actor wearing lightweight mockup air cylinders (in somewhat the same manner as an actor carrying an empty suitcase or wearing an empty camping backpack).

Nations with military diving groups

See List of military diving units.

See also

Further reading


  1. US Navy (2006). "19". US Navy Diving Manual, 6th revision. United States: US Naval Sea Systems Command. p. 13. Retrieved 2008-06-15. 
  2. Chapple, JCB; Eaton, David J. "Development of the Canadian Underwater Mine Apparatus and the CUMA Mine Countermeasures dive system.". Defence R&D Canada. Retrieved 2009-03-31. , section 1.2.a
  3. Aristotle, On the Parts of Animals, ii, 16), transl. by W.Ogle, London, 1882, p. 51:
    “Just then as divers are sometimes provided with instruments for respiration, through which they can draw air from above the water, and thus may remain for a long time under the sea, so also have elephants been furnished by nature with their lengthened nostril, and, whenever they have to traverse the water, they lift this up above the surface and breathe through it.“
  4. Thukydides, History of the Peloponnesian War, edition Ambrosio Firmin Didot, Paris, 1842, book 4, 26, and b. 7, 25. In Greek and Latin.
  5. Pierros D. Nick, The tactics of the enemies in the sea warfare during the Peloponnesian War. 1st Pan-Corinthian Congress, Corinth, Greece, 2008. In Greek. N. Pierros is a Civil Engineer and author of historical essays.
  6. The original Pirelli patented rubber 1930's diving suit
  7. Manuale Federale di Immersione - author Duilio Marcante
  8. Short history of A.R.O. from HDS Italy part 2 Pdf
  9. Short History of A.R.O. from HDS Italy part 1 Pdf
  10. History of the rebreathers
  11. Pirelli ARO WW II
  12. History of A.A.R.S. Apparecchio Autonomo Respirazione Subacquea
  13. Teseo Tesei e gli assaltatori della Regia Marina author Gianni Bianchi
  14. Shapiro, T Rees (18 February 2011). "Christian J. Lambertsen, OSS officer who created early scuba device, dies at 93". Retrieved 16 May 2011. 
  15. Lambertsen's patent in Google Patents
  16. 16.0 16.1 Shapiro, T. Rees (2011-02-19). "Christian J. Lambertsen, OSS officer who created early scuba device, dies at 93". The Washington Post. 
  18. 18.0 18.1 Perry, Tony (2013-11-03). "John Spence dies at 95; Navy diver and pioneering WWII 'frogman'". Los Angeles Times.,0,5696985.story#axzz2lqGne5YD. Retrieved 2013-11-27. 
  19. Vann RD (2004). "Lambertsen and O2: beginnings of operational physiology". pp. 21–31. PMID 15233157. Retrieved 2009-03-25. 

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