A fascinating bit of wartime propaganda, Action in the North Atlantic was apparently authentic enough in its sailing and battle sequences that it served as a training film for the merchant marine, whose work it celebrates. Even if it hadn't been technically accurate, though, it would surely have provided something of a morale boost to any sailor about to ship out.
Although the narrative zips along fairly briskly, with most of the running time on the high seas, the construction is a little awkward, flipping between tense, violent confrontations with German submarines and scenes of banter over cards or dinner that seem drawn from a rather looser film. The shifts in tone aren't as jarring as in Bogart's earlier wartime flick All Through the Night, although those more lighthearted sequences could certainly have been tightened.
As propaganda, the film is most successful in depicting the scale of the war effort and its international character: the script by future-blacklistee John Howard Lawson emphasises particularly the cooperation between Americans and Russians. The sequence of a truly multinational fleet in port in Canada is genuinely moving, capturing the sense that many individuals had of participating in something far bigger than both themselves and the flags to which they generally paid allegiance.
Although there's little distinctive in most of Lloyd Bacon's filmography, save perhaps the ability to keep the action moving swiftly along, he handles the scenes of combat extremely well. There's real nervous energy in the nighttime scenes as the freighters move through dangerous waters, while he emphasizes the often horrific character of war at sea. The cutting back and forth from freighter to U-Boot is especially effective, while the extended chase sequence by a German "wolf pack" ratchets up the tension. Despite the propagandistic tone, the Germans in that sequence are surprisingly human, depicted as a highly professional crew whose suffering is both real and distressing, as if implicitly trying to distinguish between "Germans" and "Nazis" (interestingly, the film has all of the German characters speak their native language, and does not translate their words). Bacon does a good job, too, of capturing the claustrophobia of life both above and below the waves, with several striking shots, particularly one of Bogart moving through a shipboard corridor that Bacon holds an extra second or two.
On land, the greatest interest is an appearance by Ruth Gordon, then in the second, very brief, phase of her screen career: after Action in the North Atlantic she disappeared from movie screens until her late-1960s/early-1970s renaissance. The real-life daughter of a sea captain herself, she's quite good in her brief appearance as a captain's wife, a sequence that emphasizes the comfort and stability of home in quick, subtle strokes.