This is a WWII propaganda film made to bolster the American war effort. It certainly does deserve credit for an unusual cast! In addition to familiar faces like Pat O'Brien and George Murphy, the ship they serve on has the likes of Desi Arnaz, Jackie Cooper and Max Baer (the father of 'Jethro' from "The Beverly Hillbillies" and ex-heavy-weight boxing champ).
The film surprised me a bit, as it talked about an aspect of the work of the US Navy that I'd never heard about--though it made sense. The merchant marine ships apparently also had US Navy gun crews stationed aboard them and this movie is about one of these crews. The boss is the Chief (O'Brien)--who plays his usual tough self. Murphy is an odd character--a guy who had been a Naval officer accused of cowardice who has now enlisted as a seaman--and the crew won't let him forget his past. In addition, and I know this is SUPER-contrived, but later in the film O'Brien's sister (Jane Wyatt) is taken aboard the merchant marine vessel! And, she just so happens to be Murphy's ex-girlfriend! Later in the film, a very unbelievable thing occurs. The merchant marine ship is able to easily capture a Nazi resupply ship loaded with torpedoes. And then, using this captured ship, they pass out booby-trapped torpedoes to German ships--and hilarity ensues! Not believable but really, really cool! Along the way, Murphy proves he IS a brave man and regains his good name and 1358 different movie clichés take place as well. But, because the production is so well-made and entertaining, you can't help but like the film from start to finish.
By the way, there was one problem with this film that was pretty common in films. When the ship is attacked by airplanes, they are shot down--and really crude stock footage is used. In one case, the film is very blurry and in the other a two-engine fighter-bomber becomes a single-engine plane! Pretty sloppy--and an irritant to aviation buffs like me.