A limpet mine is a type of naval mine attached to a target by magnets. It is so named because of its superficial similarity to the shape of the limpet, a type of sea snail that clings tightly to rocks or other hard surfaces.

A swimmer or diver may attach the mine, which is usually designed with hollow compartments to give the mine just slight negative buoyancy, making it easier to handle underwater.

Types of fuses

Usually limpet mines are set off by a time fuse. They may also have an anti-handling device, making the mine explode if removed from the hull by enemy divers or by explosions. Sometimes limpet mines have been fitted with a small turbine which would detonate the mine after the ship had sailed a certain distance, so that it was likely to sink in navigable channels (to make access difficult for other ships) or deep water (out of reach of easy salvage) and making determination of the cause of the sinking more difficult.

Development

Cecil Vandepeer Clarke wearing an early version of the limpet mine on a keeper plate in the position used by a swimmer.[1]

In December 1938, a new unit was created in the British military that soon became known as Military Intelligence (Research), which is sometimes abbreviated as MI(R) or occasionally as MIR. MI(R) absorbed a technical section that was at first known as MI(R)c. In April 1939, Joe Holland, the head of MIR, recruited his old friend Major Millis Rowland Jefferis as director of the technical section.[2] Under his leadership the team developed a wide range of innovative weapons.[3][4]

One of Jefferis' earliest ideas was a type of mine that could be towed behind a rowboat, which would attach itself to the hull of a ship that it passed. Getting a heavy bomb to stick to a ship reliably was a problem. The obvious answer was to use magnets, which should be as powerful as possible.

In July 1939, Jefferis read an issue of the popular magazine Armchair Science, which contained a small article on magnets:

Usage

3 views of a frogman with a Soviet-designed IDA71 rebreather set, with keeper plate to clip a limpet mine to his chest.

Second World War

One of the most dramatic examples of their use was during Operation Jaywick, a special operation undertaken in World War II. In September 1943, 14 Allied commandos from the Z Special Unit raided Japanese shipping in Singapore Harbour. They paddled into the harbour and placed limpet mines on several Japanese ships before returning to their hiding spot. In the resulting explosions, the limpet mines sank or seriously damaged seven Japanese ships, a tonnage of over 39,000 tons.[18]

An example of the use of limpet mines by British special forces was in Operation Frankton which had the objective of disabling and sinking merchant shipping moored at Bordeaux, France in 1942. The operation was the subject of the film The Cockleshell Heroes.[19]

Another case was the 1941 raid on Alexandria by six Italian Navy divers, who attacked and disabled two British Royal Navy battleships in the harbour of Alexandria, Egypt using limpet mines, having entered the harbor on the Maiale "manned torpedoes".

Limpet mines were used by the Norwegian Independent Company 1 in 1944 to attack the MS Monte Rosa. On 16 January 1945, 10 limpet mines were placed along the port side of the SS Donau approximately 50 centimetres (20 in) beneath the waterline. These bombs were to detonate once Donau cleared Oslofjord and reached open sea; however, the departure time was delayed and the explosion occurred before Donau reached Drøbak.

1970s and 1980s

In the Bangladesh Liberation War in 1971, limpets were used by rebels in Operation Jackpot. In Mongla seaport, Bangladeshi naval commandos damaged many Pakistani army support ships and gunboats.[20]

Egyptian limpets were modified by the CIA for use by the Mujahadeen in the 1979–89 Soviet–Afghan War to be attached to Soviet trucks.[21]

In 1980, a limpet mine was used to sink Sierra, a whaling vessel docked in Portugal after a confrontation with the Sea Shepherd Conservation Society.[22] Later that year, about half the legal Spanish whaling fleet was sunk in a similar fashion. There were no deaths.[23]

Limpet mines were to be used in the plan of Operation Algeciras in the context of the 1982 Falklands War. Argentine frogmen were to place limpet mines on British ships in Gibraltar but they were discovered and the plan was foiled.

Another use was the sinking of the Rainbow Warrior by French DGSE agents in the Port of Auckland on 10 July 1985, killing one person.[24][25]

2019 Gulf of Oman incidents

An example Iranian limpet mine, seen in 2015.

On 12 May 2019, four oil tankers in the Emirati port of Fujairah suffered damage from what appeared to be limpet mines or a similar explosive device. Preliminary findings of the investigation by the UAE, Norway, and Saudi Arabia concluded in June 2019, show that limpet mines were placed on oil tankers to explode as part of a sabotage operation.[26]

On 13 June two subsequent blasts in the Straits of Hormuz damaged a Japanese and a Norwegian tanker, and were blamed on Iran by the U.S. military. A video was released which, according to the United States, shows an Iranian vessel removing an unexploded limpet mine from the starboard side of the Japanese vessel, several meters forward of the damaged area.[27] The implications of an Iranian attack are disputed by the owner of the Japanese vessel and the Japanese government. The mines seemed to have been placed many feet above the waterline.[28] The vessel's crew reported an unknown object flying towards them, then an explosion and a breach in the vessel. After this, the crew witnessed a second shot.[29]

2025 Mediterranean incidents

On 24 February 2025, Reuters reported that two oil tankers in the Mediterranean, which had recently called at Russian ports, had suffered damage consistent with an explosive device such as a limpet mine.[30]

On 27 June 2025, a Greek oil tanker suffered damage from a limpet mine after having left a Libyan port, the fifth ship to have been damaged in such a manner as of August 2025.[31][32]

See also

  • Hafthohlladung, a German magnetically-adhered, shaped-charge anti-tank mine

References

Notes

  1. "T 166/40: Awards to Inventors, CV Clarke, supplementary evidence". The National Archives (GOV.UK).
  2. Unattributed. Sir Millis Jefferis – New Weapons Of War (Obituary). The Times, 7 September 1963 p. 10 column E.
  3. National Archive. T 166 – Hearing 16 November 1953 – Macrae. Document 320
  4. Warwicker 2002, p. pxxiv.
  5. "World's Most Powerful Magnet". Armchair Science, July 1939, p.70
  6. John Vandepeer Clarke. "Wartime memories of my childhood in Bedford Part 1". WW2 People's War (BBC). Retrieved 2012-04-10.
  7. National Archive. T 166 — Hearing 16 November 1953 — Macrae. Document 328.
  8. 1 2 National Archive. T 166-21 Awards to Inventors — Macrae and others.
  9. Macrae 1971, p. 15.
  10. Unattributed. "Limpet Bomb Claim By Inventors — Use Of Aniseed Balls." The Times 17 November 1953 p. 4 column F.
  11. Macrae 1971, pp. 18–20.
  12. "BBC - WW2 People's War - Aniseed Balls and the Limpet Mine". www.bbc.co.uk. Retrieved 2024-05-16.
  13. National Archive. HS 9/321/8 – SOE Personnel File: Cecil Vandepeer Clarke.
  14. HS 7/28; Seaman 2001, p. 43
  15. Lovell 1963, p. 179.
  16. HS 7/28; Seaman 2001, p. 44
  17. Macrae 1971, p. 135.
  18. "Operation Jaywick". Australian Government Department of Veterans' Affairs. Archived from the original on 2012-04-22. Retrieved 2012-04-10.
  19. "Limpet". The Canvas Kayak Website. Retrieved 4 May 2012.
  20. "Operation Jackpot". Banglapedia. Retrieved 27 July 2015.
  21. Crile, George. Charlie Wilson's War: The Extraordinary Story of the Largest Covert Operation in History Grove/Atlantic, 2003. chapter 22: "Mohammed's Arms Bazar" p.318 (paperback)
  22. "Paul Watson: Sea Shepherd eco-warrior fighting to stop whaling and seal hunts". Telegraph. 2009-04-17. Archived from the original on 2009-04-20. Retrieved 2012-04-10.
  23. "The Sea Shepherd". The Sierra Campaign. Archived from the original on 2010-01-26. Retrieved 2012-04-10.
  24. Bremner, Charles (July 11, 2005). "Mitterrand ordered bombing of Rainbow Warrior, spy chief says". Times Online. Times Newspapers. Archived from the original on 2007-02-22. Retrieved 2012-04-10.
  25. "Rainbow Warrior sinks after explosion". On This Day. British Broadcasting Corporation. July 10, 1985. Retrieved 2012-04-10.
  26. "Oil tanker sabotage likely the work of 'state actor,' investigation concludes". NBC News. 7 June 2019.
  27. "Gulf of Oman tanker attacks: US says video shows Iran removing mine". BBC News. June 14, 2019.
  28. "Japan demands more proof from U.S. that Iran attacked tankers". Japan Today. 16 June 2019.
  29. Denyer, Simon (June 15, 2019). "Japanese ship owner contradicts US account of how tanker was attacked". The Sydney Morning Herald.
  30. Maltezou, Renee; Souliotis, Yannis; Saul, Jonathan (2025-02-24). "Limpet mines likely caused blasts on two tankers in Mediterranean Sea, sources say". Reuters. Retrieved 2025-08-14.
  31. Saul, Jonathan; Maltezou, Renee (2025-07-01). "Limpet mine may have damaged Greek tanker off Libya in latest unexplained attack, sources say". Reuters. Retrieved 2025-08-14.
  32. Nieves, Carlos (2025-07-04). "Limpet mine threat in the Mediterranean grows". World Ports Organisation. Retrieved 2025-08-14.

Bibliography