Argo - class submarine The " Argo " - class was a class of two coastal submarine s built by Cantieri Riuniti dell ' Adriatico in Monfalcone for Portugal but operated by the Royal Italian Navy ( ) after Portugal was unable to pay construction costs . The submarines were built in 1936 , and both served in the Mediterranean Sea at the start of the Second World War . The boats were transferred to the BETASOM German submarine base at Bordeaux in 1940 , but returned to the Mediterranean in 1941 , where both were sunk within a few days of the September 1943 Italian armistice . Ships . " Argo " . " Argo " ( pennant number AO ) was launched 24 November 1936 and completed on 31 August 1937 . " Argo " completed two unsuccessful wartime patrols in the Mediterranean before passing the Strait of Gibraltar on 8 October 1940 for an Atlantic patrol to Bordeaux on 24 October . During its first BETASOM patrol , " Argo " damaged convoy HG 47 escort on 1 December and sank a freighter from convoy OB 252 on 5 December 1940 . First Lieutenant Alessandro De Angelis was lost overboard and drowned in heavy seas as " Argo " was returning to port . The second and third BETASOM patrols from 27 February to 28 March and from 19 May to 12 June 1941 were unsuccessful . " Argo " left France on 11 October , passed the Strait of Gibraltar on 20 October , and reached Cagliari on 24 October 1941 . After refit , " Argo " patrolled off Cape Ferrat from 6 to 21 April and off Cap Caxime ( Algeria ) from 22 to 29 May 1942 , where it sustained damage from aerial attacks requiring another period of repairs . After patrolling off the Balearic Islands from the 15 to 26 October and off the island of Galite ( Tunisia ) from the 29 to 30 October , " Argo " entered the Bay of Bougie on 11 November 1942 to torpedo the anti - aircraft ship and the troopship " Awatea " , which had been damaged by aerial bombing during Operation Torch . " Argo " then patrolled off the north African coast from 17 December to 8 January 1943 , and during February , April and June . After two patrols off Sicily in July , " Argo " was refitting at Monfalcone until the armistice of September 8 , 1943 . " Argo " was scuttled when German troops captured the shipyard on 10 September . " Velella " . " Velella " ( pennant number VL ) was launched 18 December 1936 and completed on 1 September 1937 . " Velella " was on patrol in the eastern Mediterranean when Italy declared war . After refit at La Spezia , " Velella " sailed on 25 November 1940 and passed the Strait of Gibraltar on 1 December for an Atlantic patrol to Bordeaux on 25 December . After four unsuccessful Atlantic patrols , " Valella " returned to the Mediterranean on 24 August 1941 . After refit at Cagliari and training at Pula , " Velella " patrolled without success south of Cape Palos ( Spain ) in April 1942 , south of the Balearic Islands in June , along the Tunisian coast in July , and west of the Island of Galite in August , south of the Balearic Islands in September , in the Gulf of Philippeville and the Bay of Bona in November , north of Cape de Fer in April 1943 , and off eastern Sicily in July . Its last patrol was off Salerno , where it was torpedoed by on 7 September 1943 . There were no survivors .