Cary Grant initially accepted his role in Houseboat (1958) because he was dating Sophia Loren, whom he was madly in love with. After she married someone else, Grant, heartbroken, wanted to back out. He couldn't, but the director made sure the production was a smooth one.
Carlo Ponti obtained a Mexican divorce from his first wife and married Sophia Loren by proxy, while she was in Hollywood, filming Houseboat (1958) - and dating co-star Cary Grant (17 September 1957).
Original screenplay was written by Betsy Drake, Cary Grant's wife. Grant originally wanted it to star her but his extra-marital affair with Sophia Loren complicated the project. Drake's script was drastically re-written by two other writers to accommodate Loren and bears little resemblance to Drake's concept.
Parts of the movie, Houseboat, were filmed in Fort Washington, Maryland on the Potomac River and Piscataway Creek at the present site of Fort Washington marina.