Naval Lieutenant Jerry Richards is developing a high-speed, torpedo-carrying boat, but cannot perfect the design, so he seeks the aid of top speedboat racer and designer Speed Brennan. Egotistical Speed was Jerry's roommate at Annapolis but has had ill will toward the Navy ever since he was kicked out of the academy for committing reckless pranks. Speed arrogantly refuses Jerry's request for help but reconsiders when he meets Gloria Tyler, Jerry's girl friend and the captain's daughter. Hoping to win Gloria's favor, Speed agrees to work on the project and moves to the base with his mechanic, Gloomy Kelly, and their monkey Jinxie. Speed devises a catamaran-style design for the boat, which Jerry builds despite Speed's nagging doubts that it lacks something. A week passes as the men build a model to test before a high-ranking Naval committee, and finish the night before the test run. Jerry badgers Speed into agreeing to make the trial run with him, as the boat requires two pilots, and then the pair go to a celebration party. Speed is greeted by Ethel, the wife of racer Joe Falcon, who thanks Speed for earlier helping Joe. Jerry sees Ethel give Speed a grateful kiss and misinterprets the gesture, so later, when he finds Speed kissing Gloria, he loses his temper and the men fight. The captain interrupts the fisticuffs and tells Speed to leave immediately. Gloomy is angered by Speed's grandstanding behavior and denounces him when Speed refuses to ask the captain for a second chance. The next day, Gloomy replaces Speed in the test run, but Speed's prediction about the model not being ready is proven correct when it crashes and Gloomy and Jerry are seriously injured. Onboard a plane to visit Gloomy, Speed is given an idea by its ailerons, which he believes will solve the boat's design problem. Gloomy is at first hostile to Speed but is quickly taken up by his ideas. Speed persuades Gloomy to steal the former model's torpedo so that he can include it in the new design. Gloomy is caught during his theft attempt, but once he explains the situation to Tyler, the captain aids him, and soon Speed is hard at work. Working night and day, Speed, Joe and Gloomy finish the new model and are ready to demonstrate it while Tyler tests a new torpedo for visiting senators. Speed and Joe wait at a distance as the test begins, but when one of the torpedoes goes wildly out of control, they demonstrate both their bravery and the perfection of the boat by exploding the torpedo safely away from the spectators. Tyler rewards Speed with a citation for bravery and a commission in the naval reserves. Once again a Navy man, Speed restores his friendship with Jerry and prepares to marry Gloria.