Anti-frogman techniques

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The achievements of WWII frogmen, and later events, showed the need to guard against attacks by frogmen on important bases and facilities.

Also, public availability of sport scuba gear has caused real or supposed needs in some places for underwater security of valuable underwater objects and underwater archaeology sites and of shellfish fishing stocks.

In most scenarios nowadays the intruders will likeliest be civilian sport divers, or former civilian sport divers who have turned to work diving, but in war or semi-war conditions they may be enemy frogmen attacking or spying.

On a very small scale, the term "anti-frogman precautions" could be taken to include inshore fishing villages trying officially or unofficially to exclude or keep track of visiting scuba divers which are seen as an alleged threat to shellfish stocks or otherwise adversely affecting the work of the fishing village.

The Russian PDSS system is an example of an anti-frogman defence system which includes frogmen trained in underwater fights.

The MSST (Maritime Safety and Security Team) is a United States Coast Guard harbor and inshore patrol and security team that includes detecting submerged divers.

Contents

Sport divers and underwater security

Keeping underwater security against frogman intrusion has been complicated by the expansion of sport diving since the 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.

Some naval people object to civilian divers getting into waters being used for armed forces exercises, or intruding into what in former times had been accessible only by navy and work divers. In former times civilian diving was only for work and needed Standard diving dress and big easily-seen surface support, but sport scuba diving has changed that. Around 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 in the sea offshore; some of the coastal land there is a Ministry of Defence secret area.

Another result of sport diving is a risk of civilians independently re-developing, and then using or selling without secrecy cover, technologies until then kept as military secrets, such as technical advances in underwater communications equipment. (For a 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 fairly easy to detect because they dive from land or from a surface boat, rarely or never from an underwater craft, and should broadcast their presence for their own safety.

Detection

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.

Ultrasound detection

Artificial intelligence and electronic neural networks and developments in ultrasound have made possible specialized diver-detector sonars. Examples are:-

UPSS IAS

The UPSS is Underwater Port Security System: see these links:-

http://www.military.com/NewsContent/0,13319,uscg1_031405.00.html
http://www.stevequayle.com/News.alert/05_Terror/050318.port.security.html
http://www.cnn.com/2005/US/02/02/port.security

UPSS includes the UIS and the IAS:-

UIS = Underwater Inspection System is a system of divers and ROV's who search for underwater security threats.
IAS= Integrated Anti-Swimmer System is a US Coastguard underwater ultrasound anti-diver system. For information, see http://diver.net/bbs/messages5/49352.shtml and http://diver.net/bbs/messages5/49353.shtml. IAS includes:-
SM2000 = "Underwater Surveillance System" is a search sonar, and underwater warning loudspeaker, and an underwater shockwave emitter that can force divers to surface, or stun or kill them. For information see
* http://www.naval-technology.com/contractors/sonar/kongsberg/kongsberg4.html
* http://www.naval-technology.com/contractors/sonar/kongsberg/press1.html
* Kongsberg Mesotech

And see [If you are a scuba diver, your records have been turned over to the F.B.I.]

Cerberus

This is a blue egg-shaped ultrasound device to detect submerged divers. It can distinguish a diver from a seal or dolphin or porpoise. Its range is about 700 meters. It was unveiled at UDT2003. It 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. See [this link] and [this link].

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.

Ultrasound weapon

One well-known method is a powerful blast from a ship's ordinary navigation sonar, which deranges the diver's inner ear and makes him dizzy and disoriented 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 method imitates nature; some think that the sperm whale can make ultrasound so powerful that the whale routinely uses it to stun prey.

The UPSS/IAS diver-detecter sonar system includes an underwater shockwave emitter: see #UPSS IAS.

Electric shock

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

Mechanical devices to capture submerged divers

Such devices occur in fiction, commonly in comics. Some sorts might be possible if designed.

The grab and suction types would likely be mounted on a dredging-type craft or a small submarine, and (according to type) might be also used for small-scale dredging or to recover submerged objects.

Net

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

Grab

This type has been seen in fiction.

A text story (The Deep Range by Arthur C. Clarke) mentioned a diver-catching grab used to recover a work diver suffering from nitrogen narcosis rather than to arrest a suspect.

Grab-type devices on various scales are very commonly used in nature underwater by animals. The device is usually its jaws, but in some animals evolution converted legs into arms to handle objects; see Opabinia for a very early example of a nose turned into a grab.

Suction

A suction device might make an area suction effect in the open, or might be a suction tube extended at the frogman, who may be sucked against an opening and so held, or may be sucked inside.

This has happened in reality as a diving accident among work divers (e.g. being sucked against a water outlet, or accidents in suction dredging.)

Such devices on a small scale are sometimes used in nature to catch prey: for example by the seahorse and the pipefish, and the bladderwort plant. The mouths of many teleost fish have a strong suction component to the way they work.

Anti-swimmer netting

This is metal chain-link netting placed underwater, preventing entry into an area, or at least delaying the frogmen while they cut through it.

There is a report that sometimes such netting is electrified.

Sending other frogmen against them

Often, a simple way of countering unknown frogmen or other divers is for a police force or navy base personnel to send their own frogmen to investigate. Combat divers undergo weeks of fulltime underwater training which vastly contrasts with the amount of aquatic training the average civilian sport diver undergoes; and they would be at full armed forces fitness even before the frogman training starts: see Frogman#Frogman training. Superior underwater combat training would likely decide which two groups of frogmen would win; generally, criminal or terrorist frogmen only have access to types of training which are available to civilians, or at least inadequate facilities.

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 not much accurate information on what combat between frogmen (or between other divers) underwater has happened in the real world (except for small-scale police-type arrests, for example as described in the previous paragraph). See Russian commando frogmen under "1970 and after" for a report of a real underwater fight between a guard squad of Russian PDSS frogmen and intruding enemy frogmen.

See Frogman#Equipment for features useful in equipment of frogmen who may get into underwater fights.

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 is said that this device was abandoned because of fears that wild dolphins might imitate and start harassing ordinary divers. But see http://www.flagshipnews.com/archives_2003/aug212003_11.shtml for dolphins used as an anti-frogman patrol.

[This link] reports that in 1970 to 1980 trained dolphins killed 2 Russian frogmen who were putting limpet mines on a USA cargo ship in Cam Ranh bay in Vietnam. After that, Russian PDSS frogmen were trained to fight back against trained dolphins, and in an incident on the coast of Nicaragua PDSS frogmen killed trained anti-frogman dolphins.

Prevention

Preventing public access to frogman-type diving gear, or to any diving gear

Siebe Gorman had a policy in Britain until around 1956 of keeping aqua-lung prices too high for most civilians to afford; legal restrictions on exporting currency stopped people from importing cheaper foreign aqualungs. See Timeline_of_underwater_technology#Public interest in scuba diving takes off for how this barrier broke down.
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. Or it could have been 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.

Preventing public access to diving water

One method is merely to try to stop all divers from reaching water, or stopping them from using boats, in some particular place or area. Such a bylaw may be instigated by the military to keep sport divers away from secret underwater sites, or by inshore fishermen to stop alleged poaching of shellfish.