The crew of the submarine chaser assume that Harkness is Regular Navy. Her chief boatswain's mate, Chief Larrabee (Millard Mitchell), and her chief machinist's mate are the only experienced seamen aboard. "PC-1168"'s crew are all newly inducted civilians, and her officers recently commissioned "90 day wonders". The exec, Lt. (j.g.) Barron (Eddie Albert), is a good-natured idea-man whose knowledge of seamanship is out of books. The engineering officer, Ens. Barbo (Jack Webb), has no training, education, or experience in engineering. And the supply-Mess officer, Ens. Dorrance (Richard Erdman), is plagued by seasickness.