Croisières pour Couples en Chaleur (1980)

Guillaume rents a house-boat with his wife Dominique and "their" lover, Martine. In the evening, Guillaume tells stories to put them to sleep. On their holiday cruise along a canal, they meet several characters and have 'fun' with them each time - the woman lock keeper, a girl on a bike who plunges into the canal as she waves at them, a girl who hitches a lift from a bridge and a girl who seems to be a nun, until her black stockings and suspenders are revealed. Eventually, Martine brings M. Léon on board and the film ends with an orgy.