10 August 2013 | rob-du
A few notes on rarely-seen warships in the film
This is one of very few films shot partly at the submarine base in Groton, CT, aka Submarine Base New London, CT.
A few naval combatants rarely seen in Technicolor are visible in the early part of the film. The PT boats seen near the beginning are the 77-foot Elco type. The submarine primarily featured as the fictional USS Corsair is the experimental USS Marlin (SS-205), with a conning tower modified to resemble her sister USS Mackerel (SS-204). A few O-class and R-class submarines, built in World War One and used for training in WW2, are visible in the background of some shots. For wartime security reasons, no submarine classes used in combat in WW2 appear in the film. The USS Semmes (AG-24 ex-DD-189) is seen in one shot; there are probably not many good Technicolor views of a four-stack destroyer available today. The Semmes was being used as a sonar testbed at the time.
I personally did not like how the love story progressed, as Tyrone Power is consistently deceptive and gets the girl anyway.
Another reviewer has assumed that the Nazi base would have to be near New England on the basis that WW2 submarines had a short range. This is incorrect. US submarines in WW2 routinely went from Pearl Harbor to Japan's home waters, patrolled for several weeks, and returned to Pearl Harbor on a single tank of diesel fuel. A Gato-class submarine could cover 11,000 miles without refueling, thus could have patrolled in German home waters while based in Groton if necessary. My assumption is that the Nazi base would be in Greenland, not likely given the realities of the war, but the raid on it still makes for good action.