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 (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.
Eccentric charter skipper Jim Carnahan (Wilde) and his team of hard-luck dreamers battle sharks, bandits and their own greed to recover sunken treasure off the coast of Honduras.
Marine scientists prepare to leave their underwater Oceanlab after an extended stay performing oceanographic research. An underwater earthquake interrupts their plans. Dr. Andrews (Walter Pidgeon) enlists experimental sub captain Adrien Blake (Ben Gazzara) to survey the damage and rescue the oceanauts. He brings along Chief Diver "Mack" MacKay (Ernest Borgnine) and Dr. Leah Jansen (Yvette Mimieux), fiancée of one of the scientists. Blake finds the lab has been ripped from its moorings and has tumbled down an unexplored, deep ocean trench, presumably intact. With the lab's reserve air supply dwindling, the team descends into the unexplored trench and finds an incredible ecosystem populated with monstrously over-sized fish. After surviving encounters with unfriendly denizens, they find the lab partially intact, the surviving scientists breathing from scuba tanks, and fending off giant, hungry eels. All but one of the scientists are rescued, and the submarine returns to the surface.
In the closing days of World War II, Irishman Murphy (Peter O'Toole) is the sole survivor of the crew of a merchant ship, Mount Kyle, which has been sunk by a German U-boat, which then machine-gunned the survivors in the water. Murphy makes it ashore (to a missionary settlement on the Orinoco in Venezuela) where he is treated by a pacifist Quaker doctor, Dr Hayden (Siân Phillips).
Three men (Dr. Ken Tashiro, Dr. Jules Masson, and Perry Lawton) are trapped in a bathysphere due to seismic activity. They are rescued by the crew of the supersubmarine Alpha, captained by Craig Mackenzie (Cotten), who they learn is over 200 years old (and that the Alpha was launched in the early 19th century). Mackenzie takes them to Latitude Zero to deal with the serious injuries of Dr Masson. While returning to Latitude Zero, they are attacked by a rival supersubmarine, the Black Shark, captained by Kuroi, who works for a rival of Mackenzie, Malic, who is also over 200 years old and has a base at Blood Rock.
Reynolds plays Caine, a gunrunner who becomes stranded in a small port in the Red Sea. He meets a seductive woman who propositions him to dive into shark-infested waters off the coast for scientific research. However, when Caine realizes the woman and her partner are actually treasure hunters, the action starts to heat up both above and below the water.
The film begins with Commander Bolton and a few surviving crew members of his 50-man submarine Gauntlet swimming ashore after unsuccessfully attacking German battleship Lindendorf. After a review, Captain Bolton is cleared of any wrongdoing and placed in charge of a small group of experimental X class submarines. His mission is to quickly train crews to man the submarines and sink the Lindendorf while it is hidden away in a Norwegian fiord.
A satellite reenters the atmosphere and ejects a capsule which parachutes to the Arctic, coordinates 85N 21W (approx 320 miles WNW of Nord, Greenland, in the Arctic Ocean ice pack). During an ice storm, a figure soon approaches, guided by a homing beacon, while a second person secretly watches from nearby.
Survival Devices, Inc are an organisation that employ a team of adventurers known as "the Flying Fish" who are adept in sky diving, scuba diving and martial arts. They are engaged to rescue a captured scientist imprisoned on a Caribbean island by a dictator.
Three very likeable losers fail while they pursue individual goals. Roland Darbont (Lino Ventura) is an inventor who has designed his own engine. Manu Borelli (Alain Delon) on the other hand is a pilot who prepares a spectacular stunt. Both of them are running tests on Darbont's premises when they are joined by Laetitia Weiss (Joanna Shimkus), an artist who builds abstract statues from scrap metal. They nourish each other's hopes and learn to get along with each other.
Lieutenant Ted Jackson (Elvis Presley) is a former U.S. Navy frogman who divides his time between twin careers as a deep sea diver and nightclub singer. Ted discovers what he believes could be a fortune in Spanish gold aboard a sunken ship and sets out to rescue it with the help of go-go dancing yoga expert Jo Symington (Dodie Marshall) and friend Judd Whitman (Pat Harrington, Jr.). Gil Carey (Skip Ward), however, is also after the treasure and uses his girlfriend Dina Bishop (Pat Priest) to foil Ted's plans.
A World War II-era German submarine missing for 20 years is retrieved in the Bahamas by diver Mark Brittain, hired by the wealthy Rosa Lucchesi and her partner, Vic Rossiter, who have been searching for Spanish galleons.
The United States and the Soviet Union have both developed technology that can miniaturize matter by shrinking individual atoms, but only for a limited amount of time, depending on how small the item is miniaturized.