Utmost had a successful fighting record before disappearing in November 1942. The proposed explanation is that the Italian torpedo boat Groppo detected and depth-charged her southwest of Sicily on the return to Malta. The cause remains a theory in this account. A submarine's advantage depends on concealment, and discovery becomes especially dangerous when it has spent its weapons or is damaged and trying to escape.
Chapter · 6:52:37-6:53:38
Utmost: a successful patrol and a probable depth-charge loss
Utmost's disappearance is linked to a possible attack by Groppo while returning to Malta, illustrating the danger once a submarine is detected.