From Academic Kids

Frogman is a popular term for a scuba diver. The word arose around 1940 from the appearance of a diver in shiny wetsuit and with large fins on his feet. The term preferred by scuba users is 'diver', but the word persists in usage by non-divers, especially in the media, to refer to professional scuba divers in organizations such as the police.


Military Frogmen

There may be intergrades between combat divers and other divers, such as when naval work divers (called "Clearance Divers" in Britain) are the nearest available divers to call on to investigate intruding unidentified divers and if necessary use force to make them surface: in most scenarios nowadays the intruders will likeliest be civilian sport divers. While checking for mines, naval work divers may confront the force who laid the mines.

Nations and other groups who use or used frogmen

Italy was the first nation to use frogmen: see manned torpedo. Britain soon followed.

Germany used frogmen in WWII, including in an underwater attack on canal lock gates in Antwerp after the Allies captured Antwerp in 1944.

The USA used frogmen in the war in the Pacific against Japan. That need was shown by the heavy USA casualties in the landing on Tarawa where they did not send frogmen in first to covertly survey the coast. Many USA WWII frogmen were recruited from breath-holding divers who dived for abalones for a living on the west coast of the USA.

In Britain, police divers are or were often called "police frogmen". The first British police diver was a policeman who, needing to search underwater for evidence or a body, did not use a drag but went home and fetched his sport scuba gear. And see Ian Edward Fraser.

Many nations and some irregular armed groups use or have used combat frogmen. It is reported that Israel's combat frogmen are among the most effective compared to their numbers.

It has been said that "sport diving experience is not necessarily an advantage in a frogman trainee, because sport diving encourages a casual tourist-type attitude to being underwater, and it can be difficult for the frogman-trainer to overwrite this with a disciplined attitude of doing the job and not getting distracted by such things as pretty fish or a desire to explore any shipwreck found.".


Breathing Sets

Frogmen on covert operations use rebreathers because open-circuit scuba produces large amounts of bubbles and noise (both on exhalation, and the intake hiss of the regulator valve as the diver breathes in) disclosing the diver's position. Also, rebreathers give much longer dive times for the same size of breathing set. There have been experiments with making the released air or gas come out through a diffuser, to break the bubbles up; that may work with the small amounts of gas that are released by rebreathers sometimes; but open-circuit scuba releases so much gas at every breath that a diffuser big enough to handle it without making breathing difficult would be overly large and would interfere with streamlining. Also, in any sort of underwater combat a man with a large aqualung has a high rotation-inertia and is very unstreamlined in rotating and in swimming, and his maneuvering is slowed critically compared to a man with a light streamlined rebreather with all parts close to his body. Frogman's rebreathers should be fully closed-circuit, not semi-closed circuit sets that emit a small but steady trail of bubbles, unless it has a diffuser. They should be as silent as possible in use. A fullface mask letting the frogmen talk underwater is useful. The breathing sets need to 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. Another useful feature is to 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.

Frogman's rebreathers are streamlined for long fast swimming, and may lack safety features such as a bailout that would add bulk such as would be found on work diver's sets. They should have a long dive duration. The front of the frogman's abdomen should be clear so he can climb in and out of small boats or over things.

They sometimes use open-circuit scuba during training.

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


Most frogmen use a fullface mask instead of separate mouthpiece and mask. The older type of British frogman's and naval diving mask was fullface and had a mouthpiece inside it.

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


Another problem with a frogman operating on land, is the awkwardness of walking in land in fins, unless he plans to discard his kit and return to base by some other way than by diving, which includes operations when the frogmen plan to take and hold a position on land or in a boat or ship until other troops arrive. Some sport diving fins have the blade angled downwards for more effective swimming; but this makes walking on them on land even 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 can clip them to his kit; there has been mention of a type of fin with a lockable hinge which on land can be unclipped to let the fin blade hinge up out of the way of walking. 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.

Tools and weapons carried underwater

Weapons that can be carried by a frogman include:

  • Knife. The standard weapon is a diver's knife.
  • A speargun has been seen advertized in circumstances strongly pointing to it being intended for combat and not for fishing.
  • See APS underwater rifle.
  • Other tools include net-cutters.

Transport for frogmen

In WWII Italian and British frogmen used manned torpedoes to carry them to their targets.

There are or were other sorts of underwater vehicles of various sizes for carrying frogmen to site. One example is the Subskimmer. Another is a full-sized or midget submarine such as the X-craft which frogmen can exit and return. Another is a large powerful version of the common sport-diving diver-tug. There are others, such as the Protei 5. See Diver Propulsion Vehicle.

Some frogmen are trained to parachute in to their site of operation. The backpack box of the Russian IDA71 frogman's rebreather has two metal clips to fasten to a parachute harness.

Types of frogman operation

See under manned torpedo for a list of operations using manned torpedoes. There have been many underwater diving operations in WWII and after that did not use manned torpedoes and are not on that list.

Types of frogman operation include:-

  • Sabotage: This includes putting limpet mines on ships.
  • Covert surveying: Surveying a beach before a troop landing.
  • Amphibious assualt: Covertly reaching a site and attacking it either as a raid or an advance party to hold a position for later troops.
  • Covert underwater work: recovering underwater objects. Covertly fitting monitoring devices on underwater communication cables in enemy waters.
  • Investigating unidentified divers: or a sonar echo that may be unidentified divers. This may result in an underwater arrest or fight.
  • Checking vessels and structures for sabotage: the counter to the first category. If the inspection divers find a culprit underwater during this, this category may merge into the previous category.

Anti-frogman precautions

The achievements of WWII frogmen showed the need to guard against frogman attacks. This need overlaps sometimes with underwater security of valuable underwater objects and of shellfish fishing.

Frogmen versus sport divers

The problem of underwater security has been complicated by the expansion of sport diving since mid 1950's, making it bad policy for most democracies to use potentially lethal methods against any suspicious underwater sighting or sonar echo in areas not officially closed to sport divers. Any routine patrol investigation of all "unidentified frogman" reports would have had to stop after the 30th or 50th consecutive such report proved to be civilian sport divers not in a military area. And there is a need to protect some areas underwater from intruding civilian divers. At Swanage in Dorset in England in the 1970's there were reports of incidents of naval divers being hostile towards civilian sport divers that they encountered underwater.

Another result of sport diving is of civilians independently re-developing, and then using or selling without secrecy cover, technologies until then kept as military secrets (such as underwater communications equipment). (For an incident of loss of secrecy caused by independent civilian duplication (though not underwater), see Exocet#The Lokata.)

In the inter-ethnic crisis in Cyprus in 1974 a tourist was arrested for suspected spying activity because "frogman's kit" was found in his car: it was actually ordinary sport scuba gear.

There have been incidents which have demonstrated poor underwater security, when a sport diver with a noisy bubbly open-circuit scuba and no combat training entered a naval anchorage and signed his name on the bottom of a warship. Concern at the risk of increasing the sport diving public's ability to penetrate harbors undetected, and of unofficial groups equipping combat frogmen from the sport scuba trade, might have led to the events listed below under Prevention.

Legitimate civilian divers are normally easy to detect because they dive from land or from a surface boat, rarely or never from an underwater craft, and broadcast their presence for their own safety.


Relying on eyesight from land or from surface patrol boats

In WWII this was the main precaution. That is why WWII manned torpedo operations tended to happen by night around new moon when there is the least amount of moonlight.


Artificial intelligence and electronic neural networks and developments in ultrasound have made possible specialized diver-detector sonars. An example is Cerberus (, which is semi-intelligent and reportedly can detect an air-filled chest cavity underwater and let its operator tell whether the echo is from a man's or something irrelevant such as a seal's or dolphin's.

Anti-frogman weapons

Some anti-frogman weapons are:

Depth charge

A depth charge is effective, but may cause other damage underwater, and is not recommended in peacetime when the victim may be an intruding civilian sport diver, although it is alleged to have been common practice for some years after 1945 in British naval harbors.


One well-known method is a powerful blast from a ship's ordinary navigation sonar, which deranges the inner ear and makes him dizzy and disorientated and tends to force him to surface, or may make him panic and lose his mouthpiece and drown.

There have been speculations about underwater ultrasound guns, even about them making an ultrasound beam that can disintegrate a diver into the water except the metal parts of his kit. Around the 1970's there were reports among sport scuba divers from offshore from a Ministry of Defence area in Dorset in England of diver deaths, mass deaths of fish, and divers returning reporting "strange sonic noises": they speculated about a secret anti-frogman weapon, but it may have been merely a powerful modulated ultrasound beam intended to communicate with distant submarines. This link ( describes various real-world uses of powerful ultrasound including as an anti-swimmer (= anti-frogman) weapon.

This method imitates nature; some think that the sperm whale can make ultrasound so powerful that the whale routinely uses it to stun prey.

Sending frogmen down to investigate or arrest or attack

One method which does not involve "shooting first and looking afterwards" is to send frogmen or other divers down to investigate. Frogmen and other Armed Forces divers undergo weeks of fulltime training and must be at full Armed Forces training and discipline at the start. That contrasts with the amount of training and exercise the average civilian sport diver undergoes. That is likely to decide the result when the intruder is a civilian, or a terrorist or criminal frogman-trained in secret in inadequate facilities. All or some combat frogmen are trained in underwater fights against opposing frogmen.

France has police divers trained to arrest unauthorized or suspect divers underwater and to force them to surface. One common offence there is spearfishing while using breathing apparatus.

Large underwater fights between two squads of opposing frogmen have been seen at least twice in fiction films (Thunderball, and The Silent Enemy), but there is no useful information on what combat between frogmen (or between other divers) underwater has happened in the real world, except for police-type arrests as described in the previous paragraph.

Electric shock

There have been reports of underwater electric shock weapons mounted on warships to defend them from frogmen. This device imitates nature; see electric eel and electric ray.

Mechanical devices to capture submerged divers

There have been cases of a fishing trawl being used or recommended by naval men as a useful way to get unwelcome or unauthorized divers out of the water.

Apart from that, I have not heard in the real world of any such thing as a dredging-type craft or a small submarine equipped (e.g. with a grab or suction device) to capture submerged divers, but such a device may be possible.

Anti-swimmer netting

This is metal chain-link netting placed underwater.

Trained animals

A reported anti-frogman guard is or was dolphins trained to carry on the nose a device which injects a large amount of compressed carbon dioxide into the frogman. It is said that they were trained at Point Mugu. It was said that this device was abandoned because of fears that wild dolphins might imitate and start harassing ordinary divers.


Here may be included attempts at restricting the types of kit available in the public diving kit trade:-

  • Siebe Gorman's policy in Britain until around 1956 of keeping aqualungs too expensive for most civilians to buy, until British diving clubs started making their own aqualungs, and then Submarine Products Ltd. designed a new type of regulator not covered by the Cousteau-Gagnan patent and made aqualungs and sold them at an affordable price; later the Cousteau-Gagnan patent time-expired and any firm could legally copy it.
  • The Subskimmer, which is useful for covert underwater penetration, took decades to develop and passed through at least three firms and is still too expensive for sport divers and sport diving centers. This may be due to interference from Ministries. Equally it could be a commercial decision: the market for sports use was judged to be too small.
  • Siebe Gorman consistently refused to sell rebreathers to the civilian public. Mixture rebreather development was kept away from the public eye and the sport scuba trade until the end of the Cold War in 1991.

With civilian sport-type divers, one method is merely to try to stop them from reaching water in some particular place or area.

Derivative word usages

  • Some scuba diving clubs have an entry class called "Tadpoles" for younger children who want to start scuba diving.
  • British Navy men have a slang term "pond life" to mean civilian sport divers.

Errors about frogmen

  • 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.
  • Some say that some stone carvings show ancient Assyrian frogmen with crude breathing sets. But the so-called breathing set was merely a goatskin float used to cross a river, and its so-called breathing tube was merely to inflate it with.
  • In comics there have been thousands of drawings of combat frogmen and other covert divers wrongly shown using two-cylinder twin-hose open-circuit aqualungs, even anachronistically in stories set during WWII when aqualungs were unknown outside Cousteau and his close associates. All real covert frogmen use rebreathers.

External links

Please provide some links, someone. And/or a list of frogman operations.


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