In the middle of summer in Viareggio, Marcello, a fallen nobleman who is too old to show off his fashionable clothes according to the judgement of his companion and employer Alba, decides to court the young Foschina, who reciprocates his interest and is the sister of Manolo, an old friend found by chance on the coast.
Manolo, a swimming instructor and worshipper of the foreign tourists who crowd the beaches of Versilia, tries unsuccessfully to organise an aerial advertisement with the help of his pilot friend Cittelli. Along the seafront, there is Yvonne, a street vendor selling sweets, who wins the heart of Francisco, a cyclist of modest success, and the two eventually stay together.
Manolo also has a second sister, Selena, engaged to Nardoni, a strict military man who finds himself unwillingly attracted to Gigì, a French woman he believes to be a transvestite. Frightened by the situation, Nardoni eventually decides to marry, only to discover later that Gigì is actually a woman.
In the meantime, Foschina returns to her fiancé after discovering Marcello's true profession, who has been recalled by Alba, who had threatened to fire him. In the end, all these stories find a kind of happy ending in their own way.