Upon rising one nice, sunny day, ultra-wealthy Rollo Treadway glances out his mansion window just as a newlywed couple drives by in a car. Rollo decides to get married too, having nothing else to do that particular day. He tells his butler to arrange a honeymoon cruise to Honolulu, and then is driven across the street to propose to his beloved, the Ship Owner's Daughter. When she promptly rejects his proposal, Rollo decides to go to Hawaii alone.
Elsewhere in the city, foreign agents from a small nation purchase the Ship Owner's boat, the Navigator, docked at Pier 12. Scheming enemy spies from yet another small country plan to kidnap the captain and first mate and then set the ship adrift, so it will be destroyed on the rocky shore. Under a cover of darkness, the saboteurs carry out their dirty deed. When the Navigator's former owner returns to retrieve some papers from the ship, he is inadvertently caught up in the kidnap plot. Rollo then mistakenly arrives at Pier 12 instead of Pier 2, boards the empty ship and goes directly to his cabin, unaware of the commotion. The girl, upon hearing her father's screams, hurries onto the boat to look for him, before the spies send the ship to its fate.
The next morning, Rollo realizes that he's alone on the drifting ship. The girl also thinks no one is on board, until she sees a flicked cigarette butt that Rollo has just tossed down to the deck below. Frantically, she calls out to the mysterious person, and Rollo answers her. The pace quickens as they narrowly miss each other while racing around the ship's three decks. She goes to the boiler room below, while he rests on the upper deck's vent pipe. Suddenly, he falls through the pipe to the boiler room below, where the girl is quite astonished to see him. Not missing the chance, Rollo once again asks her to marry him. And, once again, she turns him down.
Their first day at sea turns out to be an adventure in ineptitude, since neither has ever entered a kitchen before. Using cooking utensils and pots made for banquets, and drinking seawater coffee, the discouraged couple soon finds that survival means learning how to adapt. Coping with life on deck is even worse as Rollo and the girl take an unexpected swim in the ocean, and he wrestles with a collapsing deck chair. Nightfall brings its hazards too. A menacing-looking photo of the captain frightens them, as the rocking ship causes doors to slam in unison and a phonograph to start playing a recording of "Asleep in the Deep." While trying to get some sleep on the deck, they're drenched by a passing thunderstorm, and finally head back inside where it's dry.
A week later, Rollo and the girl prove that necessity is the mother of invention, as they master life at sea by turning the huge kitchen into a breakfast nook for two, complete with gadgets ala Rube Goldberg, and the ship's coal furnaces into cozy, decorated sleeping quarters. It's smooth sailing until the ship's propeller breaks on the ocean floor, just as they spot an island that happens to be inhabited by hungry cannibals. The girl convinces a very nervous Rollo to don a deep-sea diving suit and go under water to fix the problem. While Rollo putters away in the ocean deep, repairing the damage and fighting off swordfish and an octopus, the natives storm the ship, cut Rollo's return hose, and steal the girl.
Rollo realizes that something is wrong. He floats to the surface and emerges out of the water like a space alien, causing the cannibals to run away in fear. Using his inflated dive suit as a raft, the two paddle back to the ship. Once on board, they fight off the invading cannibals with firecrackers, rockets, and a miniature cannon that is more intent on shooting Rollo than the enemy. Finally, the couple abandons ship for a small canoe that quickly capsizes. Thinking all is lost they kiss and sink below the water's surface. Suddenly, they emerge on top of a Navy submarine, much to the surprise of the sub's crew. They scramble for safety inside the hatch where the girl proclaims her love for Rollo, who in turn, sends the submarine into a spin. — Janice Agnello