From July to December 1941 the submarine was based at Malta from where she carried out interception patrols with the 1st Flotilla.

[1] During 1941 she carried out patrols off Azores in defence of HG convoys on passage to and from Gibraltar, and with Olympus for patrol of Oran to intercept Vichy Dunkerque reported to about to attempt passage to France during Operation Principal.

On 14 August 1941 she was involved in a friendly fire incident, when the submarine Talisman under the command of Lt.Cdr.

M. Willmott, RN mistook her for an enemy submarine and fired several torpedoes at her, approximately 140 nautical miles (260 km; 160 mi) north-west of Alexandria (position 32°41'N, 27°35'E).

Favell, RN, Otus unsuccessfully fired a torpedo at an unidentified enemy armed merchant cruiser of 4000 tons, approximately 175 nautical miles (324 km; 201 mi) east of Valletta, Malta.