The Castaways of Turtle Island (1976)

Bonaventure (Pierre Richard) is a semi-competent travel agent who makes up stories about his great romantic adventures to tell to the girls in his office. One evening, he meets a woman who has the same name as one of his made-up romances, and they share a for-real one-night encounter. Afterward, he thinks up a scheme for a unique tour situation in which people might pay for a limited-time visit to a completely undeveloped island where they will be forced to become modern-day Robinson Crusoes.