The first "Mexican Spitfire" entry of 1942, Mexican Spitfire at Sea is set mainly on a Hawaii-bound ocean liner. Combining business with pleasure, vacationing advertsing man Dennis (Charles "Buddy" Rogers) hopes to sign a contract with a wealthy client. Alas, these plans are scotched by the well-meaning idiocies of Dennis' peppery spouse Carmelita (Lupe Velez), and by a whole flock of Dennis' relatives who have invited themselves along for the voyage. Once again, it's up to Dennis' Uncle Matt (Leon Errol) to save the day-which inevitably requires old Matt to disguise himself as his British lookalike Lord Epping. Marion Martin, the blonde bombshell who'd caused so much trouble in the previous series entry Mexican Spitfire's Baby (1941), is seen in a minor role.