Captain Crowther (Sid James) has five of his crew replaced at short notice before a new cruise voyage begins. Not only does he get the five most incompetent crew men, including the first officer Majoribanks (Kenneth Williams), the medical officer Dr Arthur Binn (Kenneth Connor), the head chef Wilfred Haines (Lance Percival), the barman Sam Turner (Jimmy Thompson) & the captain's valet Tom Tree (Cyril Chamberlain), ever to sail the seven seas, but the passengers turn out to be a rather strange bunch too. The ship's crew includes Young Officer (Ed Devereaux) and a cook (Mario Fabrizi).The head chef is forever seasick. The first officer is late for duty on account of oversleeping, the medical officer is not very good. The 5 newcomers decide to try their best to impress the captain, as that would put them in consideration for a job on the new liner. But, even if one newcomer fails, all will be painted with the same brush. The SS Happy Wanderer is the cruise ship and after this voyage, Crowther hopes to get a job as captain on a transatlantic ship, promising the crew members their jobs will be safe under their new captain. Starting off from England, the Happy Wanderer calls at unnamed ports in Spain, Italy, and North Africa before going home again. The captain assigns all the regular paperwork to Majoribanks. This includes Health reports, Dock reports, Crew reports, Food reports, Log reports, Sports report, Diesel Oil & Fuel reports.Single ladies Gladys (Liz Fraser) and Flo (Dilys Laye) take the cruise, with Flo hoping to find a husband. Bridget (Esma Cannon) is her usual dotty and entertaining self, and one unnamed passenger (Ronnie Stevens) never disembarks but always goes straight to the bar to drink, to forget an unidentified woman. The crew and passengers settle in as the ship leaves port.Gladys and Flo fall for the PT instructor Mr Jenkins, but nothing comes of it, especially when Flo turns out to be hopeless in the gym. Flo ends up unconscious and is taken to Binn for treatment. Binn gets tangled with her while checking Flo's heartbeat, and that's when Crowther walks in for an inspection and finds Binn and Flo on the floor, tangled with each other. Meanwhile, the new men try to impress Crowther, but disaster follows disaster with him getting knocked out and covered in food at a party.Crowther is missing his favorite drink, the Aberdeen Angus that only his regular barman knew the recipe for. Crowther orders several bottles of liquor in his office as he tries to guess the recipe by trial and error. Binn and Majoribanks think that the captain is drunk on the job and Binn announces to all the officers that Majoribanks must take over the ship. But that's when Crowther walks in fit and fine, and Majoribanks faints.Flo and Bridget get drunk and Gladys has to force Flo away from the bar. Flo runs into Binn on the way back to her cabin and has a dance with him, which the captain watches. He knows that Sam got Flo drunk in the middle of the afternoon and that's why she is dancing with Binn, who has eyes for Flo.Meanwhile Flo, who is looking for a husband, decides to go for the captain & makes strange cooing noises every time he is around. Crowther discusses the situation with his first officer Majoribanks, who convinces him that the captain's rough face has scared Flo. Crowther summons Flo to assure her that he is her friend, but is terrified to learn that Flo is infatuated with him. He wants nothing to do with Flo.Majoribanks turns psychoanalyst for the ship's officers, including the captain. He makes the captain understand that his deep-rooted dislike for the new hands is due to his fear for change & his love for stability. The captain appreciates this insight. Meanwhile, ship's doctor Dr. Binn (Kenneth Connor) has fallen for Flo, but she wants nothing to do with him, so he serenades her with a song after leaving Italy (Bella Marie, sung by Roberto Carinali), which she does not hear as she is asleep. Gladys, who has heard the song, realizes that Flo is in love with Binn and with the help of First Officer Marjoribanks arranges a plot for Binn and Flo to get together. Gladys kisses Binn and thanks him for serenading her. This makes Binn realizes that Flo doesn't even know his feelings for her. It works and the confident Binn finally confesses his feelings to a gobsmacked Flo, who returns his affections.Crowther lets the five newcomers know that they have improved since the cruise began, simply by doing their jobs and not by trying to impress him. Crowther says that he wont taken them with him to the new liner but would recommend them to his successor on the current ship. They learn that the captain has overseen the Happy Wanderer for ten years and decide to hold a surprise party for him, with the passengers. Haines bakes him a many-flavored cake and the barman cables the former barman for the recipe of the captain's favorite drink, the Aberdeen Angus.The party goes well, and Crowther gets his telegram telling him he has the captaincy of the new ship. He turns it down as he recognizes it does not have the personal touch of a cruise ship and prefers the company of his own crew.