Wikipedia Says: Houseboat is a 1958 romantic comedy film starring Cary Grant, Sophia Loren, Martha Hyer, Paul Petersen, Charles Herbert and Mimi Gibson. The movie was directed by Melville Shavelson, who also directed the original 1968 version of Yours, Mine and Ours.
Grant’s wife Betsy Drake wrote the original script, and Grant originally intended that she would star with him. After he began an affair with Loren while filming The Pride and the Passion, Grant arranged for Loren to take Drake’s place with a rewritten script for which Drake did not receive credit. The affair ended in bitterness before The Pride and the Passion’s filming ended, causing problems on the Houseboat set. Grant hoped to resume the relationship, but Loren agreed to marry Carlo Ponti instead
Thanks to ShantyboatLiving.com reporter Dan Hohman.