After seeing the movie, John Gibbons, a herpetologist (reptile scientist) at the University of the South Pacific, realized that the iguanas that appeared in the film were a distinct species that had never been seen or documented by scientists before. Afterwards, Gibbons visited Nanuya Levu, the Fiji Island where the movie was made, and named the species the Fiji Crested Iguana.
It was the director's original concept to have the two grown characters play the entire film in the nude, which scared off many actors (including Jennifer Jason Leigh, who was the first choice for the female lead.) After Leigh passed on the project, the producers offered Diane Lane and Willie Aames the film after screen-testing them together in Mexico, where Lane was shooting a western...but the pair discussed the nudity together after the crew left and called a few days later to say they wouldn't do the film, either. With shooting set to begin in a matter of days, the desperate director agreed to let Shields make the film predominantly clothed, with a body double employed for the nude scenes. With that settled, the casting director returned to the thousands of audition tapes they'd made over the course of a year, and decided Christopher Atkins would be alright if he permed his hair to look more "savage."
The double for Chris Atkins was initially one of the seaplane pilots flying staff and crew from the Fiji mainland to the island where the movie was shot. He did most of the nude scenes with Brooke Shields's double as well as a few of the minor stunts.
Although the movie received lukewarm reception in the United States and was panned by a lot of critics, it is a highly popular nostalgic movie in some former socialist countries (like Romania and Hungary), as well as in Brazil, and is frequently reran on television.
The trivia item below may give away important plot points.
Gus Mercurio, who played the First Mate at the end of the film who said, "No, sir, they're asleep," after finding Emmeline, Richard and Paddy's boat, also appeared at the beginning of Return to the Blue Lagoon (1991). In the sequel, he's the First Officer on the ship who picks up Paddy (renamed Richard) and gives him to Lisa Pelikan.