Gangland boss Joe Kalhari, working with Ricki Hart, operator of a swamp-side dive in the Okefenokee swamp aside the Georgia-Florida border, rules an empire of smugglers who run dope and undesirable aliens into the United States, uses seaplanes at the primary mode of transportation. Searching for his sweetheart,Lowheeya, who has been lured into the shack of Pully, a Kalhari henchman, airplane pilot Chick Osceola, finds evidence of the smuggling operation.

Marine Lieutenant Steve Landers has perfected a new bomb-release for airplanes which he is testing with the aid of his mechanics,'Singapore' Stebbins and Jack Murray. Dick Weber, one of a group of enemy agents attempting to steal the plans, is a friend of Colonel Dale, whose daughter, Linda, is engaged to Landers. Weber learns that "Singapore" and Jack are to deliver the final blueprints to the Colonel's home. Beckstrom , head of the spy ring, has some of his agents dress as Marines and obtain entry the the hangar. They get the plans but "Singapore" and Jack have overheard a conversation that indicates the spies are heading for a nearby island which is the headquarters of the espionage group.