While scuba-diving near shipwrecks off Bermuda, vacationing couple David Sanders (Nick Nolte) and Gail Berke (Jacqueline Bisset) recover a number of artifacts, including an ampoule of amber-colored liquid and a medallion bearing the image of a woman and the letters "S.C.O.P.N." (meaning "Santa Clara, ora pro nobis" or "Saint Clara, pray for us") and a date, 1714. Sanders and Berke seek the advice of lighthouse-keeper and treasure-hunter Romer Treece (Robert Shaw) on the origin of the medallion, who identifies the item as Spanish and takes an interest in the young couple. The ampoule is noticed by the man who had rented diving equipment to Sanders and Berke, which in turn attracts the attention of Henri 'Cloche' Bondurant (Louis Gossett, Jr.), a local drug kingpin for whom the shop owner works, who unsuccessfully tries to buy the ampoule and then begins to terrorize the couple with Haitian black magic. The ampoule contains medicinal morphine from the Goliath, a ship that sank during World War II with a cargo of munitions and medical supplies. The wreck of the Goliath is considered dangerous and is posted as off-limits to divers due to the danger of explosions. Treece concludes that a recent storm has exposed her cargo of morphine and unearthed a much older wreck containing Spanish treasure.
Treece makes a deal with Cloche, so they can dive in peace making him believe he will get the ampoules for a million dollars, while his real plan is to have the chance to find the treasure. Cloche gives him three days to recover them. Sanders, Berke, and Treece make several dives to the wrecks, recovering thousands of morphine ampoules from Goliath and several additional artifacts from the Spanish wreck. Adam Coffin (Eli Wallach), the only survivor from Goliath, joins to help in the boat, but his loyalty is not very clear. When they are attacked by sharks, Coffin only says that he probably fell asleep without noticing they were in trouble.
Through research in Treece's library, they reconstruct the history of the lost treasure ship, locate a list of valuable items, including a metallic jar with the letters "EF" engraved on it, and learn the identity of the noblewoman for whom they were made by the king of Spain. Sanders is determined to locate at least one item on the list to establish provenance, since without it there is no value to the treasure. Treece wishes to destroy the Goliath to put the morphine out of reach of Cloche, and Cloche interferes with their efforts so that he can recover the morphine for himself. During a running series of conflicts, Treece's friend Kevin (Robert Tessier) is murdered by one of Cloche's henchmen. Adam betrays them and is killed when he triggers a booby-trap while trying to steal the recovered morphine. A climactic battle during the final dive ensues, with Cloche and his divers being killed in the destruction of the Goliath and the recovery of a gold dragon necklace that will provide the needed provenance of the treasure.
The original storyline was developed from a Bermuda shipwreck, The "Constellation", which sunk in 1942, carrying ampules of morphine among other war cargos such as concrete and pharmaceuticals.
Two actors from the Jaws films (which were also based on a novel by Peter Benchley) appeared in this film. Robert Shaw played shark hunter 'Quint' in Jaws in 1975, while Louis Gossett, Jr. would later go on to play SeaWorld park owner 'Calvin Bouchard' in Jaws 3 in 1983.
Filming began in July 1976 with open water diving sequences near Peter Island, the location of the real shipwreck of the RMS Rhone in the British Virgin Islands. Robert Shaw was paid $650,000 plus a percentage of the profits; Bissett and Nolte were paid $200,000 each.
The film's score was composed by John Barry, who at the time was most famous for his work on the James Bond film series. In the same manner of a Bond film, Barry collaborated with a high profiled singer for the film's theme song. American singer Donna Summer teamed up with Barry for the film's signature song entitled "Down Deep Inside (Theme From The Deep)". Summer was a singer under contract to the film production company, Casablanca Record & FilmWorks. The song was nominated for a Golden Globe Award and a hit on the U.S. Dance Chart, as well as a top-five singles hit in the UK, and a top-forty hit in the Netherlands. Vincentian calypsonian Alston 'Beckett' Cyrus contributed the song Disco Calypso to the soundtrack, and his album of the same name was distributed by Casablanca as a result.
The Deep was released on June 17, 1977 and was well received by the public, making it the eighth-highest-grossing film of 1977. Critics' reviews, however, were largely negative. The film currently holds a 36% "Rotten" rating at the review aggregation website Rotten Tomatoes based on 14 reviews.
Vincent Canby of The New York Times gave the film a negative review, stating that "The story, as well as Peter Yates's direction of it, is juvenile without being in any attractive way innocent, but the underwater sequences are nice enough, alternately beautiful and chilling. The shore-based melodrama is as badly staged as any I've seen since Don Schain's The Abductors (1972), which is to remember incompetence of stunning degree."
Upon its release, the film was noted for its opening scene of Jacqueline Bisset swimming underwater while wearing only a thin, white T-shirt and a black bikini bottom. Producer Peter Guber claimed this helped make the film a box office success, and said "That T-shirt made me a rich man."
The film was nominated for one Academy Award and one Golden Globe Award:Marvel Comics: The Deep (November 1977)