I love this film genre, as did my father, a USN WW2 vet (not in the Silent Service.) DT was made during the war and released when the outcome was still in doubt. I'd put it a notch below "Run Silent, Run Deep" a 1957 sub sage starring Gable and Lancaster and I would say the biggest reason is that Robert Wise brought RSRD in at 93 minutes, with virtually no wasted scenes while Delmer Davies brings DT in at a bit bloated 2:15 that could have easily had at least .20 minutes edited from without ruining the story.
Cary Grant, in a solid dramatic performance plays a veteran sub commander who receives an assignment to take his sub into Tokyo Bay shortly after the 12/7/41 attack to do surveillance and collect information for the Doolittle Raiders, whose attack on Tokyo was successfully carried out the following April. This is where the plot has some holes – by listening to dialogue from the veteran crew on board the USS Copperfin you would assume that this boat and crew has already completed several war patrols and they are departing Alameda Naval Base on Xmas Eve, 1942. Another huge gaffe?the crew is heading to Tokyo via the Aleutian Islands, where they will engage in a dangerous rendezvous with a USN PBY who is delivering Lt Ridgely, Naval Intelligence officer, who is fluent in Japanese and familiar with Tokyo. Ridgely will be leading a commando unit onshore to collect data. So why in the world isn't the USN just placing him on board the boat when they depart the base? Except it does allow the script writers to put in an exciting air attack from Jap fighter planes that leads to the death of a crewman, a funeral at sea and several speeches by crew about why we are fighting this war.
There are a couple of flashback scenes that are really needless, but DT pays off with some top notch drama that captures the tension and camaraderie of a sub crew, plus some terrific action when Grant and his crew have to fight their way out of Tokyo Bay and sustain a lengthy depth charge attack. Some good performances by familiar faces playing crew members, among them John Garfield as a perpetually horny sailor, Dane Clark, Robert Hutton and WB veteran Alan Hale, as always playing everyone's best pal? whether he was on the prairie, in Sherwood Forest or on the seas.