Operation Algeciras was an aborted Argentine plan to sabotage a Royal Navy warship in Gibraltar during the Falklands War. The Argentine assumption was that if the British military felt vulnerable in Europe, they would decide to keep some vessels in European waters rather than send them to the Falklands.
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The plan was to launch divers from Algeciras, have them swim across the bay, to Gibraltar, under cover of darkness, attach the mines to a British naval ship and swim back to Algeciras. The timed detonators would cause the mines to explode after the divers had time to safely swim back across the bay. The plan was foiled when the Spanish police became suspicious of their behavior and arrested them before any attack could be mounted.