True as a Turtle is a 1957 British comedy film directed by Wendy Toye and starring John Gregson, Cecil Parker, June Thorburn and Keith Michell. In the film, a young couple embark on a voyage on a ketch named "Turtle". John Coates wrote the screenplay, based on his novel of the same name.
The voyage was made on a sailboat.
A ketch is a type of sailboat so  it is true they made the voyage on a sailboat. Sailboat wasn't used in the description so the system only sees ketch, not the definition.