The Boca Ciega Bay home of Dr. Chester and Doris Babat was rented by the production and renovated for filming of the pool scenes with a makeshift temporary structure built over their outdoor pool. The homeowners later built a permanent pool house based on the film's exact design, where they still relax decades later.
Actor Brian Dennehy was arrested for driving under the influence on a night out with Steve Guttenberg during filming of the movie - after a night in local police station he thanked the officer responsible.
Ron Howard's brother, mother and father all appear in the film. His wife appears also, as a receptionist/nurse behind a desk, and she was pregnant with twin daughters at the time. The reception area desk was used to hide that fact.
According to Ron Howard, several members of the cast liked to get into hypothetical discussions about the chance their characters were offered in the film. Maureen Stapleton was dead against it, while Don Ameche said he'd be the first in line.
The music used for part of the sequence when the Coast Guard and the police are chasing the boat is nearly the exact same music used in Star Trek II: The Wrath of Khan (1982) when Spock is in the engine room trying to fix the warp drive. James Horner did the music for both films.
The tinted map Walter gives to Jack showing him the underwater location of their search for cocoons is actually an infra-red aerial photograph of Bay County, Florida (where Panama City Beach is located) printed on a transparency.
The film marked the first collaboration between director Ron Howard and composer James Horner. Horner would go on to compose the music for many films directed by Howard, including Willow (1988), Apollo 13 (1995), How the Grinch Stole Christmas (2000) and A Beautiful Mind (2001).
Director Ron Howard had originally wanted Joan Bennett for the role of Bess MCarthy, but since she had been talked out of taking the role by her fourth husband, David Wilde, the role was offered to Gwen Verdon instead.
Clint Howard appeared as an Alien in Star Trek The Original Series episode, The Corbomite Maneuver as Balok in 1966 . He appeared in Star Trek Enterprise as Muk , a Ferengi in the episode Acquisition (2002)