View source for Defense against swimmer incursions

{{Short description|Methods of protection from incursions by divers and swimmers}}
{{Use dmy dates|date=October 2023}}
{{Multiple issues|
{{original research|date=April 2012}}
{{unreliable sources|date=April 2012}}
{{more citations needed|date=May 2017}}
{{Lead too short|date=April 2020}}
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'''Defenses against swimmer incursions''' are security methods developed to protect [[watercraft]], [[port]]s and installations, and other sensitive resources in or near vulnerable [[waterway]]s from potential threats or intrusions by [[swimmer]]s or [[Scuba diving|scuba divers]].

==Risks and threats==
The need for military underwater security was demonstrated in [[World War II]] by the achievements of [[Frogman|frogmen]] against armed forces facilities such as the [[Decima Flottiglia MAS#Combat record|Italian frogman actions in WWII]]. Since the late 1950s, the increasing demand for and availability of sophisticated [[scuba diving]] equipment has also created concerns about protecting valuable underwater [[archaeology]] sites and [[shellfish]] fishing stocks.<ref name="seaguard" />

The 12 October 2000 [[USS Cole bombing]] was not carried out by underwater divers, but did bring renewed attention to the vulnerability they present for naval ships. Divers can swim 100 to 200 yards in about three minutes, and large [[sonar]] ranges would be required around ships for security forces to detect underwater swimmers in time to make an effective response.<ref name="nlsn" /><!--Non-lethal Swimmer Neutralization Study page 7-->

In March 2005 the [[Philippine military]], while [[interrogating]] a captured anti-government [[terrorist]] [[bomber]], found that two of [[Southeast Asia]]'s most dangerous terrorist organizations linked to [[Al Qaeda]] were said to be jointly training militants in scuba diving for attacks at sea.<ref name="Anderson 2005" />

Swimmers can approach from the surface or underwater, each presenting its own detection and deterrence challenges. The interception and apprehension of intruders detected in bodies of water pose unique safety risks.<ref name="nlsn" />{{clarify|what are these unique safety risks, who are at risk?|date=July 2020}}

Zones of operations include:
* Underwater.<ref name="nlsn" />
* At the surface of water.<ref name="nlsn" />
* In small boats.
* In larger vessels.
* Apprehension of suspected frogmen onshore, before or after they dive.

Potential theaters of operation:{{citation needed|date=May 2017}}
* In an enclosed security area, e.g. a harbor.
* In open water to protect submerged artifacts (usually undersea [[archaeological]] sites).
* In open water (often on a [[frontier]]) to prevent [[smuggling]].
* In open water to protect sea life. (This, on a small scale, may be defined to include various known unofficial actions by inshore [[fishermen]] to protect their shellfish stocks.) <!-- This is reality. In the 1960s there was an amount of trouble in UK and USA waters between scuba divers and lobster fishermen. -->

==Recreational divers and underwater security==
Maintaining underwater security against intrusion on or under the water has been complicated by the expansion of [[recreational scuba diving]] since the mid-1950s, making it unacceptable in most democracies to use potentially lethal methods against any suspicious underwater sighting or sonar echo in areas not officially closed to recreational divers. Routine investigation of all "unidentified frogman" reports would be swamped by reports of recreational divers who were not in military areas.{{Citation needed|date=December 2010}}

For a long time it would be easy for diving professionals and other experienced divers to distinguish a sport diver with an [[open-circuit scuba]] such as an [[Aqua-lung|aqualung]] from a combat frogman with a [[rebreather]]; and 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 willingly advertise their presence for their own safety;<ref name="Whitten" /> but recent multiplication in sport [[rebreather]] use may have changed that somewhat.{{citation needed|date=May 2017}}

In the past, when scuba diving was less common, many non-divers—including police, patrol, and guards—knew little about diving and did not know of this difference in diving gear, but described all divers as "frogmen". One result was an incident in the inter-ethnic crisis in [[Cyprus]] in 1974 when a tourist was arrested for suspected spying because "frogman's kit" was found in his car; it was ordinary sport scuba gear.{{Citation needed|date=December 2010}}

After about 1990, the rapid growth in the number of sport diving rebreather brands has clouded this distinction, while advanced sport divers increasingly tackle longer, deeper, riskier dives using equipment once available only to armed forces or professionals. This means that even techniques for trapping them underwater, disorienting them, or forcing them to the surface would be an unacceptable risk to civilian divers' lives.{{Citation needed|date=December 2010}}

Another result of sport diving is a risk of civilians independently re-developing, and then using or selling on the free market, technologies, such as technical advances in underwater communications equipment, formerly kept as military secrets.{{citation needed|date=May 2017}}

There have been incidents which have demonstrated poor underwater security, such as when a sport diver with a noisy, bubbly, [[Scuba set#Open circuit|open-circuit scuba]] and no combat training entered a naval anchorage and signed his name on the bottom of a [[warship]].{{Citation needed|date=December 2010}}

==Detection==
The MSST ([[Maritime Safety and Security Team]]) is a [[United States Coast Guard]] harbor and inshore patrol and security team who specialize in Naval Security.{{Citation needed|date=August 2009}}

Besides the visual detection by guards, a number of other systems are also used by security forces to prevent infiltration by frogmen.

===Underwater===
;Ultrasound detection
:[[Artificial intelligence]] and electronic [[neural network]]s and developments in [[ultrasound]] have made possible specialized diver-detector sonars.{{citation needed|date=May 2017}}

Examples of diver-detecting active sonar systems are:
* {{annotated link|AN/WQX-2}}
* {{annotated link|Cerberus (sonar)}}
* {{annotated link|Underwater Port Security System}}

;Trained animals
:Trained [[dolphin]]s and [[sea lion]]s can find submerged divers. Both can see, and hear direction of sound, well underwater, and dolphins have natural [[sonar]].<ref name="nlsn" />{{rp|3}}
:The United States Navy’s MK6 [[Marine Mammal System]] is supported by [https://web.archive.org/web/20061007023826/http://enterprise.spawar.navy.mil/ SPAWAR] and uses dolphins to find and mark mines and divers in the water. This system was used in:
:* Vietnam in 1970{{En dash}}71.{{citation needed|date=May 2017}}
:* Persian Gulf in 1987–1988.{{citation needed|date=May 2017}}
:* [[San Diego]] harbor for security during the 1996 [[Republican National Convention]].{{citation needed|date=May 2017}}

;Remote-controlled underwater vehicles
:A [[remotely operated underwater vehicle]] (ROV) could search for submerged divers; but ROVs are expensive to run, and as technology is now could not attack several targets one after another as quickly as a marine mammal.<ref name="nlsn" />{{rp|13}}
:An underwater ROV needs to be controlled. It could find and identify divers, and perhaps deter them. It should not be easily overpowered or attacked or outpaced by the suspect divers. If it is to attack the suspects, it should carry a suitable weapon.{{Citation needed|date=August 2009}}

[[File:Aa owlrov 01.jpg|thumb|right|"OWL"-type surface ROV (also known as the Unmanned Harbor Security Vehicle) used to search for submerged divers]]

;Surface ROV
:A surface ROV can move on its own and scan below itself with sonar, but without a long-range weapon it can do little against deeply submerged suspect divers.{{citation needed|date=May 2017}}{{Original research inline|date=May 2017}}

==Surveillance of civilian divers==
A few sources claim the [[FBI]] asked the US's largest [[scuba diver]] certification organizations to turn over the records of all divers certified since 1998; this turning-over is now done once a year.<ref name="House 2003" />

==Anti-frogman weapons==

===Sound===
{{see also|ultrasound|sonic weaponry}}
The main effects of [[ultrasound]] on the human body are [[heating]] and [[cavitation]].<ref name="nlsn" /> Analysis of research literature related to effects of ultrasound concluded that reported ultrasound-caused organ damage was associated with sound pressure levels exceeding a certain intensity threshold, regardless of frequency<ref name="nlsn" /> The [[Underwater Port Security System|UPSS/IAS diver-detector sonar system]] includes an underwater [[shock wave|shockwave]] emitter.

[[Westminster Group|Westminster International]] have implemented audible sound based defense systems.<ref name="acousticdefence" /> These systems irritate or cause pain to the target's ears. Diver aversion to [[low frequency]] sound is dependent upon [[sound pressure level]] and [[center frequency]].<ref name="Fothergill et al 2001" />

===Underwater firearms===
{{Main|Underwater firearm}}
[[Underwater firearm]]s fire a steel rod, not a bullet, for better range underwater. They are all more powerful than a [[speargun]], and can fire several shots before reloading. Their barrels are not [[rifling|rifled]]; the fired projectile is kept in line underwater by [[hydrodynamic]] effects, and is somewhat inaccurate when fired out of water.{{citation needed|date=May 2017}}

===Other underwater man-carried weapons===
* For a long time the diver's standard weapon and tool has been a heavy [[knife]].{{citation needed|date=May 2017}}
* A catalog issued in 1991 by Life Support Engineering (now Mercury Products) contained several [[military]] / [[commando]] type diving kit items and also a compressed-air powered [[speargun]].{{citation needed|date=May 2017}}
* Underwater, a [[Club (weapon)|baton]] would have to be used for thrusting or jabbing, not swung, due to water resistance, and designed accordingly. The target's [[solar plexus]] will probably be protected by his diving gear.{{citation needed|date=May 2017}}

===<!-- A lot of the material appears to be speculative. -->Trained animals===
The [[United States Navy]] has deployed [[sea lion]]s to detect [[underwater diving|divers]] in the [[Persian Gulf]].<ref name="sealions" /> The sea lion is trained to detect the diver, connect a [[Surface marker buoy|marker buoy]] to his leg by a C-shaped [[handcuff]]-like clamp, surface, and then bark loudly to raise the alarm. 20 sea lions have been trained for this at the [[US Naval Warfare Systems Center]] in [[San Diego]]. Some have been flown to [[Bahrain]] to help the Harbor Patrol Unit to guard the US Navy's [[United States Fifth Fleet|5th Fleet]]. Sea lions adapt easily to warm water, can dive repeatedly and swim up to 25&nbsp;mph, can see in near-darkness, and can determine the direction of underwater sound. In training the sea lions have been known to chase divers onto land.{{citation needed|date=December 2022}}

From 1970 to 1980 trained dolphins killed two Soviet frogmen who were putting [[limpet mine]]s on a US [[cargo]] ship in [[Cam Ranh]] bay in [[Vietnam]].<ref name="delfing" /> Subsequently, Soviet [[PDSS]] frogmen were trained to fight back against trained dolphins. In an incident on the coast of [[Nicaragua]], PDSS frogmen killed trained anti-frogman dolphins. The arrival of [[:Category:Underwater firearms|underwater rifles and pistols]] has likely reduced the threat of trained animals.{{citation needed|date=May 2017}}

Animals, unlike [[Remotely operated underwater vehicle|ROV]]s etc., need to be fed and kept in training whether they are needed at work or not, and cannot be laid aside in a storeroom until needed.

===Remote-controlled underwater vehicle, as weapon===
A [[Remotely operated underwater vehicle|ROV]], as well as searching, could be equipped to arrest or attack divers on command, but with their technology as it is could not attack several targets one after another as quickly as a marine mammal. A surface-only ROV would need a long-range weapon to be effective against deeply submerged suspect divers.{{citation needed|date=May 2017}}{{Original research inline|date=May 2017}}

==Restriction and Prevention==

===Restricting public access to frogman-type diving gear, or to any diving gear===
* [[Siebe Gorman]] had a policy in Great Britain until around 1956 of keeping prices of [[aqua-lung|aqualungs]] 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, starting with British sport divers making their own aqualungs from ex-[[RAF]] cylinders and converted [[Calor Gas|Calor gas]] regulators.{{citation needed|date=May 2017}}
* 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.
* 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. As a result, when [[North Sea Oil]] exploration started in the 1960s, the oil drilling firms needing deep-dive work had to develop [[nitrox]] diving techniques independently, from concept up, without using the [[Royal Navy]]'s know-how; and then the Navy revealed that they had used nitrox diving (which the Navy called "mixture") before 1945.{{citation needed|date=May 2017}}
* In the US, military [[rebreather]]s were not marketed to the public primarily due to cost and attendant [[legal liability]] issues. Legal issues still tend to discourage the development and sale of the rebreather in the US, though acceptance and use is growing.{{citation needed|date=May 2017}}{{Original research inline|date=May 2017}} The US military has not tried to stop sales of rebreathers to the public in the US. It has realized that recreational SCUBA has now exceeded earlier military SCUBA in quality, and hopes that a similar increase in quality and decrease in price will come from commercial-off-the-shelf rebreather equipment.{{citation needed|date=May 2017}}{{Original research inline|date=May 2017}}

===Prevention technology===
Technology exists where underwater speaker systems can be deployed around the designated area.<ref name="disruption" /> This array of speaker systems can be programmed to send high powered frequencies which then blasts powerful 'disruption' signals into the water. The frequencies have a maximum disorientation effect on the diver(s), which induce discomfort or panic causing them to leave the area or surface for interception. In cases where the divers remain in the water, the frequencies are likely to have a continued adverse effect which could cause sickness and confusion.{{citation needed|date=May 2017}}

===Preventing public access to water===
For sport divers and similar who have no means of covert entry, 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 called for by the military to keep sport divers away from secret underwater sites, or by inshore [[fishermen]] to stop alleged poaching of [[shellfish]].{{citation needed|date=May 2017}}

The US has made many such regulations to protect such [[infrastructure]] as [[power plant]] and [[nuclear plant]] water intakes and discharges, bridge foundations, harbor and pier installations, and naval facilities.{{citation needed|date=May 2017}}

[[Socialist Federal Republic of Yugoslavia|Yugoslavia]] forbade all sport diving except a few government-controlled groups, and required official permission for each campaign of archaeological or scientific diving.{{citation needed|date=May 2017}}

==References==
{{reflist|refs=

<ref name="Anderson 2005">{{cite web |url=http://www.gsnmagazine.com/may_05/underwater_security.html |title= Underwater security garners more cash & new technologies |author= Martin Edwin Anderson |date= 5 May 2005 |publisher= GSN Homeland Security Insider |archive-url=https://web.archive.org/web/20061109005722/http://www.gsnmagazine.com/may_05/underwater_security.html |archive-date= 9 November 2006}}</ref>

<ref name="disruption">{{cite web|url=http://www.wg-plc.com/international/defence/enforcer+underwater+diver+disruption.html |url-status=dead |archive-url=https://web.archive.org/web/20090406105610/http://www.wg-plc.com/international/defence/enforcer%2Bunderwater%2Bdiver%2Bdisruption.html|title=Underwater Communication & Diver Disruption System  |archive-date=6 April 2009}}</ref>

<ref name="Fothergill et al 2001">{{cite journal |vauthors=Fothergill DM, Sims JR, Curley MD |title=Recreational scuba divers' aversion to low-frequency underwater sound |journal=Undersea Hyperb Med |volume=28 |issue=1 |pages=9–18 |year=2001 |pmid=11732884 |url=http://archive.rubicon-foundation.org/2368 |archive-url=https://web.archive.org/web/20110727224529/http://archive.rubicon-foundation.org/2368 |url-status=usurped |archive-date=27 July 2011 |access-date=2008-08-12}}</ref>

<ref name="House 2003" >{{cite web |url=http://commdocs.house.gov/committees/judiciary/hju88543.000/hju88543_0.HTM |title=2003 Defense of Privacy act and privacy in the hands of the government |website=commdocs.house.gov |access-date=8 February 2008 |archive-date=31 January 2008 |archive-url=https://web.archive.org/web/20080131172620/http://commdocs.house.gov/committees/judiciary/hju88543.000/hju88543_0.htm |url-status=live }}</ref>

<ref name="nlsn">{{Cite report | title = Non-Lethal Swimmer Neutralization Study | year = 2002 | place=San Diego | publisher = SSC San Diego, United States Department of the Navy | url = http://archive.rubicon-foundation.org/xmlui/bitstream/handle/123456789/7519/ADA406644.pdf?sequence=1 | archive-url = https://web.archive.org/web/20120524072616/http://archive.rubicon-foundation.org/xmlui/bitstream/handle/123456789/7519/ADA406644.pdf?sequence=1 | url-status = usurped | archive-date = 24 May 2012| access-date=2008-02-07 | work = first Applied Research Laboratories, University of Texas at Austin}}</ref>

<ref name="seaguard">{{cite web |title=Surveillance and Protection of Underwater Archaeological Sites: Sea Guard |author=Akal, Tuncay |publisher=The Acoustical Society of America |url=http://www.acoustics.org/press/155th/akal.htm |access-date=2009-02-22 |archive-url=https://web.archive.org/web/20081115170600/http://www.acoustics.org/press/155th/akal.htm |archive-date=15 November 2008 |url-status=dead}}</ref>

<ref name="Whitten">{{cite web|last=Whitten|first=Chris|title=Dive Flag Law|url=http://www.dive-flag.com/law.html|publisher=Dive-Flag|access-date=7 July 2012|archive-date=30 March 2022|archive-url=https://web.archive.org/web/20220330034532/http://dive-flag.com/law.html|url-status=live}}</ref>

<ref name="acousticdefence">http://www.wi-ltd.com/defence/Maritime_Defence/Acoustic_Defence_Systems {{Webarchive|url=https://web.archive.org/web/20090628091804/http://www.wi-ltd.com/defence/Maritime_Defence/Acoustic_Defence_Systems |date=28 June 2009 }} Enforcer_Underwater_CommunicationDiver_Disruption_System</ref>

<ref name="sealions">{{Cite web|url=http://www.divernet.com/news/items/sealion250203.htm|title=Sea Lions Deployed to Detect Divers in Persian Gulf|archive-url=https://web.archive.org/web/20060512074525/http://www.divernet.com/news/items/sealion250203.htm|archive-date=12 May 2006}}</ref>

<ref name="delfing">{{Cite web|url=http://specialoperations.com/Foreign/Russia/Naval_Units.htm|title=Delfin (Dolphin)|archive-url=https://web.archive.org/web/20051202112154/http://specialoperations.com/Foreign/Russia/Naval_Units.htm|archive-date=2 December 2005}}</ref>

}}

==External links==
* [https://web.archive.org/web/20070929204400/http://www.mtronline.net/MTIssues/mt200607o2.pdf Marine Technology Reporter – July 2006] page 26 etseq
* [http://www.maritimeawards.ca/pdfs/Port_Security_Requirements.pdf Port Security Requirements for Industrial Opportunities]

{{Underwater diving|other}}
{{authority control}}

{{DEFAULTSORT:Anti-Frogman Techniques}}
[[Category:Armed forces diving]]
[[Category:Underwater security]]
[[Category:Special forces]]
[[Category:Frogman operations]]