The Troops of St. Tropez (1964) on Netflix

The ambitious police officer Cruchot is transferred to St. Tropez. He's struggling with persistent nude swimmers, but even more with his teenage daughter, who's trying to impress her rich friends by telling them her father was a millionaire and owned a yacht in the harbor. He gets drawn into it when he tries to cover for her when a friend 'lends' the car of her assumed father. It turns out that the real owners of the yacht aren't exactly what they pretend to be either...