Ein Kolumbus auf der Havel plot
Father Oscar buys an old sailboat named Pütz and wants to go on a sailing trip with his daughter Marianne, nicknamed Mannerl. Mother Gerda, nicknamed Doctor, would rather spend her vacation in a hotel in Bratislava, but she changes her mind. In the summer they now go on holiday on a beginner's tour to the Bolter Canal on the River Müritz. The father tells the best sailor stories. The family has a few adventures, such as a smuggling trip, a leak in the boat and heavy thunderstorms. Nannerl also gets to know the boy Mischa, who, like her, is on a boat trip with his family.