Sophia Loren's role was originally offered to 'Gina Lollobridgida', who declined.
Clifton Webb's character in the film is named Victor Parmalee. Webb's real name was Webb Parmalee Hollenbeck.
Originally, the film was to star Cary Grant. It was four days into shooting in Greece when Grant canceled. His wife, Betsy Drake, had survived the sinking of the Andrea Doria ocean liner and he went to be with her. Robert Mitchum was then considered, before Spyros Foucas signed Alan Ladd.
This is Sophia Loren's American film debut, coming out in April of 1957. Some people have reported that The Pride and the Passion is actually her first film, but that film was released in July of 1957.
While filming Boy on a Dolphin, Sophia Loren was required to walk in a trench in order to give audiences the impression that her diminutive co-star, Alan Ladd, was taller than she.