Onionhead

In the spring of 1941, Al Woods quits an Oklahoma college to join the armed forces after a quarrel with his co-ed sweetheart, Jo. He joins the Coast Guard, partly by chance due to the flip of a coin. After boot training, Al is assigned to a buoy tender in Boston, the Periwinkle, as a ship's cook although he has no cooking experience. He encounters immediate hostility from the chief of the galley, Red Wildoe, from new crew mates and cooks' helpers Gutsell and Poznicki, and from his arrogant department head, Lieutenant (junior grade) Higgins.
In a Boston bar, Al picks up Stella, who appears to do this kind of thing with some regularity. They develop a strong attraction, but she seems to be holding out for something more.[3] He befriends Gutsell by fixing him up with a girlfriend of Stella's and learns from Wildoe how to be a ship's cook, making a number of embarrassing mistakes. Al, frustrated after Stella won't spend a night in a hotel room with him, stops seeing her, whereupon he and the alcoholic Wildoe get drunk together and bond. Wildoe begins seeing Stella with Al's blessing. Pearl Harbor is attacked and war declared. Wildoe abruptly proposes to Stella and they marry. A free-for-all breaks out at their wedding celebration, with a jealous Al instigating a fight with soldiers who are clearly familiar with Stella already. Wildoe is assigned to another vessel performing convoy duty at sea. During this time, Stella begins seeing other men. Al tries to prevent this on Wildoe's behalf, but can't resist Stella himself.
Aboard the Periwinkle, Al becomes the new chief cook. Higgins, promoted to executive officer, is discovered entering lesser amounts than they pay for the cost of officers' meals into the ledger of the ship's mess and pocketing the difference. He purchases substandard food for the crew in order to keep the mess budget from showing a deficit. Higgins also objects to finding Al's hair in his food, so Al shaves his scalp bald, earning the nickname "Onionhead." Assuming erroneously that all the officers are in on the scam, Al bypasses channels to report the theft to the District Office. During leave back home to attend his father's funeral, Al reconnects with Jo, realizing that she is the one he loves. In port again, Wildoe asks Al to take Stella home from the bar one night when he is recalled to his ship. Stella tries to seduce Al, who calls her a tramp. She replies: "I can't help what I am."
The Periwinkle sinks a submarine in combat, with Al playing a major role, but his accusation of embezzlement impugns the honor of the innocent captain and exposes the ship to scandal at the board of investigation. Al declines to produce any proof of Higgins' misdeeds in order to save their reputations, but privately slips the captain the proof. In a meeting with Al and the executive officer, the captain tells Al that his punishment for an unsubstantiated allegation against an officer is loss of his rating and reassignment to Greenland, but also informs Higgins that he will have to repay every embezzled dollar before his court-martial. He gently chastises Al for not having come to him with the proof earlier, but gives him leave to marry Jo before he ships out for Greenland.

Question: What type of ship does the Periwinkle sink in combat?
Answer: Submarine