On her first patrol she sank the Italian merchant ship Ariosto of 4,116 tons off Cape Afrika, Tunisia on 15 February 1942.

Source:[1] P38 left Malta on 16 February 1942, to intercept a very important large supply convoy for Axis forces off Tripoli, Libya.

Amongst them was the Italian torpedo boat Circe, equipped with German sonar and depth charge throwers.

Shortly after 10:32 (Italian time), following a single attack in which all depth charges were dropped by Circe, P38 rose only to sink immediately again.

At 10:40 (Italian time), after further attacks with depth charges and machine guns by the escorts Emanuele Pessagno, and Antoniotto Usodimare, as well as aircraft, during which one Italian rating was killed by friendly fire, P38 rose out of the water, her propellers still turning, steering planes set to surfacing, before crashing back beneath the waves at a bow-down angle of 40 degrees.