A Woman on Fire (1969)

"How do you tell your husband you have an emptiness only another man can fill?"

Clara, the sexually frustrated wife of a businessman goes on vacation with her husband, daughter and best friend. While there, she finally learns that sex can be passionate and wonderful, something she was never able to discover with the help of her husband. Unfortunately, she learns this with a handsome lifeguard, who finally makes her succumb to his psycho-sexual games.