IN THE SEA OF CORTES -- Here off the coast of Mexico, where the mountains of Baja jut from the water in vast red rock escarpments, Jacques-Yves Cousteau's new "windship" Alcyone, with its strange aluminum sails, makes a steady 8 knots in light winds. Cousteau himself has just ducked below to the communications room when suddenly there is a great commotion and the cry goes up: "Dolphins!"

Cousteau's son Jean-Michel, who is at the helm, shouts below to his father. Soon everyone is watching as a dozen of these gentle and intelligent sea creatures speed toward the ship from off to port in their undulating way -- diving, rising, diving. It seems amazing that they can keep up, but they settle into Alcyone's wake and follow playfully for a mile or so.

"Allow me," says Jean-Michel, who has just been engaged with has famous father in a heated discussion about repairs on their other exploration ship, the legendary Calypso, "to be overwhelmed by this for a moment." He gazes out the window at the sleek black forms, then shakes his head sorrowfully at the thought of predatory yachters and fishermen. "That anybody could shoot them is unbelievable."

Minutes earlier, Cousteau was complaining to his son that someone "qualified" must be found to equip Calypso if the ship is to be ready for its July 4 appearance at the Statue of Liberty celebrations in New York. Calypso is in a Miami shipyard receiving new engines. "There is no one in whom I have confidence," the grand old man says irritably in French, throwing up his arms and turning to go below.

But the dolphins work their magic on him, too, and later, at dinner in a resort hotel on the beach, Cousteau mentions them when a young woman asks him a philosophical question about the meaning of life.

"Every day there is a surprise," Cousteau answers in his lightly accented English, settling back into a chair in the hotel's palm court under a full moon. "Yesterday night there were shadows on the mountain that gave us an impression of a Chinese painting. This morning, we had an exceptionally lively group of dolphins . . . The best way to approach happiness is expansion of yourself . . . with creation . . . with love . . . with sharing . . . with knowledge. And they are the only ways that lead to a form of happiness. If you concentrate on yourself, you're doomed, you're miserable, you're neurotic!"

Cousteau, now in his 76th year, is launching upon the most extensive, difficult exploration of his life -- the five-year "Rediscovery of the World." His two ships, with their teams of divers, scientists and cameramen, will circumnavigate the globe, producing 20 hours of television specials under a $15 million agreement with Turner Broadcasting System Inc. He and Jean-Michel, now director of the 220,000-member Cousteau Society, will shuttle back and forth from the ships to Paris, Monaco and New York, where they maintain homes and film studios.

It is to be a grand adventure. When it is completed -- this "Rediscovery" -- Cousteau will be 80 years old. At some point, he says with a grin, "I'll be switched off," Jean-Michel, now 47, is being groomed to take over.

Other stars of Cousteau's 80 films and the new "Rediscovery" series that began this month:

Dominique Sumian, the gentle bearded giant who serves as expedition leader and who has more than once saved the life of a comrade. Michel Deloire, the underwater cameraman whose blue eyes seem to drill through you in search of courage, or the lack of it. Jean-Paul Cornu, land cameraman, always with a quip and warm smile. Guy Jouas, the ship's electronics and communications engineer and premier practical joker. And perhpas the greatest Cousteau sublegend of all, Albert Falco ("First Diver of the Calypso," as the book about him is titled), who is on leave in France until he takes command of Calypso in July.

"I've been on American TV longer than anyone," says Cousteau. And he analyzes his success: "We are not documentary. We are adventure films. The kids identify with Falco on the diving saucer . . . the entire environmental content of my films is wrapped into adventure, with the same heroes . . . Dominique has been with me 21 years." He says his scientific work has "credibility," and viewers like the fact that the films show "a lot of gadgets."

Cousteau pauses and then smiles, "I never thought we would be so successful."

The Cousteau formula has been modified in various ways since those early days of "The Silent World" (1956) and later of his endless series "The Undersea World of Jacques Cousteau." Less than a third of the new Haiti film, for example, is devoted to underwater shots. For the most part the film, titled "Waters of Sorrow," is a sociological portrait of a nation that has disastrously depleted its marine and forest resources.

"This series has little to do with the behavior of animals," Cousteau says of Rediscovery." "It has to do with the behavior of people with respect to the water system."

And, increasingly it seems, the films may have a political dimension, though Cousteau vehemently insists that he has "no politics." Extensive footage of his interview with Fidel Castro will appear in the "Rediscovery" special on Cuba, and the material is sensitive enough that the old filmmaker says he has provided a transcript to the U.S. State Department as a courtesy.

"I thought it was my duty to inform them of what I did," he says. "They had nothing to do with the film."

The Cousteau formula is also being modified by the increasing influence of Jean-Michel. With his father's approval, he investigated the origins of cocaine in South America and produced a powerful documentary," "Snowstorm in the Jungle," which became part of the recent Amazon series.

Some eyebrows were raised.

"It's shocking to some of the public that says, 'What the hell is Cousteau doing with cocaine, I want to see more diving,'" says Richard C. Murphy, the Cousteau Society's vice president for science and education.

But Murphy, who spent most of the weekend here diving with the Cousteau cameramen, adds, "Many members of the society said, 'Wonderful, fantastic!" . . . Jean-Michel is a different person. His ideas don't conflict with his father's. I find it exciting to have another Cousteau also with good ideas."

Jean-Michel says he plans to take Alcyone across the Pacific to Eniwetok atoll to investigate the long-term impact of U.S. nuclear bomb tests decades ago. "What really happened?" he asks. ". . . I want to know. And we're going to find out."

A new Cousteau for the '80s, and beyond. The Fabulous Sea

Despite any changes in Cousteau's formula, the natural world in all its splendor remains his primary focus. Last weekend, the Cousteaus and their team members were constantly talking to one another about things they had seen on land and sea, and often they spoke like excited children.

"Susan, it's so dry here that the cows eat the cautus! Can you imagine it?" says cameraman Jean-Paul Cornu to Susan Richards, a Cousteau Society logistics honcho. Cornu says he's eager to film fluorescent scorpions on a nearby island, and asks Richards to ship him some black lights when she returns to New York.

"Zheek" -- Cousteau's nickname based on his initials, JYC -- also told him to be sure to film the grunions in the northern Sea of Cortes. Grunions are small fish that congregate on the beach to mate. But Cornu thought the boss had said "grognon," meaning "grumpy" in French. "I thought he was pulling my leg."

When Cornu finally found the mating grunions, people were racing dune buggies on the beach, killing them by the hundreds. He filmed this desecration for "Life of a Desert Sea," the film to be based on the two-month Sea of Cortes exploration.

"The sea here is so alive," says Jean-Michel, standing on the bridge of Alcyone. "There's no other place like this. Some places we go for days without seeing things."

As he speaks, a black fin is slicing the water behind the ship -- a giant manta, says Jean-Michel. There are flying fish, and as the ship sails toward an island off which the Cousteau diving team is working, small mantas leap out of the water in spectacular flip-flops.

"Hup! Hup!" shouts Jean-Michel.

A few weeks ago, he says, "the team was able to swim in and out of a very large school of tuna above a tuna boat wreck. They probably know it's a potentially safe area because other boats won't go near a wreck. It was a very large school, very spectacular. There were manta rays and hammerhead sharks. It's the dream dive that one looks for. Everything works. The water is clear, there's lots of fish and a shipwreck."

At the dive site, located at the base of huge cliffs rising from the sea, Dominique Sumian stands at the controls of the black rubber Zodiak boat. Bubbles from the divers boil to the surface of the water. From time to time a diver can be seen streaking below, powered by one of the team's handheld underwater scooters.

Then the divers come up, clambering into the boat, wet and panting. Sumian is everywhere, helping them lug the heavy equipment aboard.

When they return to the Alcyone, Richard Murphy, a marine biologist, is excited. "There's this little microforest and there were oysters everywhere. I didn't capture any, but they looked the type that would have pearls."

The Cousteaus have been criticized for a lack of scientific sophistication. On this expedition, for example, they arrived in the Sea of Cortes too late to film the migration of blue whales. But the Cousteaus say that their films reveal wonders that people would never otherwise see.

They are, in a sense, primarily educators. Cousteau and his son are planning Disney-like educational theme parks to be called "Cousteau Ocean Centers" in Paris and several U.S. cities yet to be designated. Norfolk city officials recently scuttled the idea there after several years of planning for it. "I'm disappointed," says Cousteau. "They don't know what they're missing. We'll do it somewhere else."

For the team members, the sea holds an endless romance. Louis Prezelin, the wiry cameraman who filmed Alcyone's recent expedition to Cape Horn -- a harrowing experience in which the ship was almost lost on the rooks -- described the Horn in these haunting words, tossed off casually at a cocktail party last weekend:

"It was beautiful in its own wild way -- rough and wild and gray. It was Cape Horn as you would imagine from novels. The sea would change from perfect calm to 50 knots of wind with no warning at all. The sea would be smoking, which makes it tricky when you go out in those little rubber boats." Gadgets, Etc.

To stand on the bridge of this "windship" is to be astonished. The 233-foot-high "Turbosails," invented by Cousteau and engineers Lucien Malavard and Bertrand Charrier, look like white aluminum grain elevators placed on deck. They are cylindrical, and with much less surface than fabric sails, and you wonder how the wind could exert much pressure on them. But they act like vertical airplane wings -- a long flap running up and down each sail and small fans that draw air past the flaps ensure that air passing the sails on the leeward side moves faster than air passing on the windward side. Result: pressure from windward to leeward.

Amazingly, this yields several times the power of normal sails. Alcyone tacks just like a sailboat, but must remain on a fairly even keel for the sails to function well.

All this runs by computer, automatically. You stand on the bridge, and the computer, which displays the functions of the ship on a color screen, talks to you. It says "automatic mode" and "manual mode" and such in a deep, tinny voice. The computer trims the sails constantly, adjusting the flaps and even rotating the entire cylinders for proper orientation to the wind. Finally, you choose the speed you want and the computer maintains it with a mix of wind power and thrust from the 102-foot yacht's diesel engines. On a voyage across the ocean, Cousteau says, he saves perhaps a third on his fuel bill.

The idea, of course, was to make megabucks for the Cousteau Society and others by marketing Turbosails to freighter comanies. But the drop in oil prices has stalled that idea for the time being.

Alcyone, which sleeps 12, is crammed with radio equipment, a telephone, telex, electronic scientific gear and even a device that receives a daily weather map from San Diego. Last weekend, there was a great deal of concern as these reports showed the year's first depression -- Tropical Storm Agatha -- forming in the ocean a thousand miles to the southeast. But the storm moved on.

Alcyone's fantail is a series of work platforms for the divers, and it is typically stacked with supermodern scuba tanks and other gear. An aluminum ramp slopes to the water so that the Zodiak work boats can rejoin the ship in motion, much as jets land on a carrier.

The living quarters below are paneled in rick dark wood.In the galley, cook John Lumb keeps plates of freshly sliced fruits and vegetables out for snacks.

Cousteau emerges from his private room, nibbles a cucumber, studies an atlas opened to the South Pacific. This being a French ship, a dozen bottles of wine are consumed each day, and assistant engineer Ange Legal, noting that the sun would be over the yardarm if there were one, pours red Bordeaux into a wine glass.

He gingerly walks the glass to the bridge, popping up from below and handing it to Jean-Michel with a bright grin. "Voici le sangre de Christ!" A Close Group

It's a dangerous business.

"With Captain Cousteau you do a lot of working to the limit of your machine," says Michael Sullivan, one of two pilots of Cousteau's seaplane. "He takes risks, but they're all calculated. We take extreme precautions." A risk Sullivan sometimes takes, he says, involves landing in "a sea bigger than you should land in."

Dominique Sumian points out that the divers are working here without an onboard decompression chamber, which Calypso has. "If we have a decompression accident," he says, "we have no backup -- and every diver knows that."

The former French naval frogman adds, "Every time we take a risk, we take them because we enjoy it! It's the seasoning of life, it makes life more interesting. When you have your adrenaline come up, afterward you feel much better."

There have been several deaths over the years -- one diver who simply didn't surface in the Great Lakes and was found dead days later, another team member who slipped on the ice in Antarctica and was hit by a helicopter blade, another killed in a car wreck in Uganda. And, of course, Philippe Cousteau, Jean-Michel's younger brother, who died in a seaplane accident in 1979.

The Cousteau Society has been lucky, says Jean-Michel, because "we've never had anybody crippled forever in tens of thousands of dives."

As he says this, Carol Hastings, who is going the advance work for the exploration here, complains that her straw hat isn't sufficiently broken in.

Jean-Michel snatches it, throws it to the floor and stamps on it.

Perhaps it is because the work is so serious, and often dangerous, and because the team must be closely knit, that there is so much practical joking. Guy Jouas once glued Jean-Michel's boots to the deck. At dinner one night last weekend, Jean-Michel got going on the subject of grunions in Mexico, which he says mate in three or four seconds in broad daylight, unlike the California variety, which take longer and do it at night. "The Mexican grunion doesn't have the same inhibitions," he said. "In Mexico you call it a quickie. I mean a real quickie."

Jean-Michel's humor can turn quickly into bitter irony. "This little sea is full of resources," he tells his guests one night in a brief speech. "And if we don't preserve them, all these people who are coming here to enjoy them will have to go somewhere else to rape nature."

Cousteau's wife of more than half a century, Simone, often lives on Calypso for long periods. Known as "La Bergere" (the shepherdess), she takes care of the team members as if they were her own children. Though she is publicity shy, and was not here last weekend, Jean-Michel says she has been one of the world's leading women divers. Jean-Michel's wife, Anne-Marie, the Cousteau Society's official photographer, is here, and Richard Murphy's wife, Pam Stacey, who edits the Society's journal, Calypso Log. There are other women, too, but few in front-line diving and camera jobs.

Jean-Michel says "We are really considering changing our views about that." Zheek!

What to make of this living legend? Over the course of the weekend, Cousteau reveals himself -- at times philosophical, at others lighthearted, spinning yarns of the sea, talking details of the film business, musing on wine (on which he claims to be an expert) and biorhythms.

He says he's not interested in money and has never been ambitious. "I'm not proud of anything," he says. "Pride is stupid. We are all sentenced to death . . . but good friends' count." Cousteau says he doesn't watch movies, because "I don't care" what other filmmakers are doing. "I think about drinking wine tonight." And, he says, he doesn't want to leave a legacy. "I just enjoy myself," he says. In 100 years, "I hope I will be forgotten -- like everybody else."

Cousteau says he feels like the ancient warriors who attacked forts out of duty, although they knew they could never win. "And that's exactly what I'm doing," he says, citing what he calls a Spanish proverb to the effect that the road to paradise is paradise.

Yet Cousteau is an intensely private man. There is no authorized biography, and he is "furious" at some of the books and articles written about him. His private life is "none of their business," he proclaims. In fact, he grows quite testy when one young visitor presses him. "I don't want you to know if I drink coffee or tea or have adventures with my secretary," he says. ". . . Out! This is my life. It's my privacy . . . hands off!"

Later he admits that he prefers tea.

Cousteau did not dive last weekend, saying that an old ear condition forces him to work into diving slowly, over a period of several days -- more time than he could spend on this trip. "At my age and with my responsibilities I don't want to be deaf," he says, adding that he will return to the Sea of Cortes in June for a week or two of diving.

Cousteau wears a dark blue leisure suit over turtleneck shirts and says he has only one tie, which he saves for dinners with U.S. presidents. He says he knew Ronald Reagan "very well" as governor of California, and "I told him, 'You are going to be president of the United States.' He remembered that, and invited me to dinner at the White House."

When Cousteau made his Cuba film, he had to wait days for Fidel Castro to appear for an interview. At one point Jouas, the joker, put on a beard and green cap, stuck a cigar in his mouth and pretended to be the Cuban leader -- much to the astonishment of the minister of fisheries, who was waiting along with Cousteau.

When Castro finally showed up and saw a photo of Jouas' antics, he laughed and autographed it for Cousteau.

As for biorhythms and jet lag, Cousteau, who continually flies all over the world, says he believes in neither. Animals, he says, sleep and eat when they want, and the only thing that makes humans feel jet lag is the "social conventions" that prevent them from doing so. The Great Adventure

It is to be Calypso's maiden voyage across the Pacific. Cousteau has sailed the oceans and rivers in the ship for more than three decades, but he has yet to visit Nez Zealand and some islands of the South Pacific.

After the July 4 celebration in New York, Calypso will pass through the Panama Canal, explore the Galapagos Islands and, helped along by the southeast trades, sail 3,000 miles west across the open sea to the Marquesas.

Then 1,000 miles southwest to Tahiti, 1,750 miles west to Tonga, 1,000 miles south to the Kermadec Islands and L'Esperance Rock, and on into Auckland in early October. Later, on to southern Australia.

Alycone, meanwhile, will finish up here in July, prowl up the West Coast of the United States and then head out into the Pacific for Eniwetok, the Philippines, Japan and other points.

Toward the end of the "Rediscovery" adventure, Cousteau hopes to sail Calypso up the Yangtze River. He began negotiations with Chinese representatives in Monaco in recent weeks and plans to continue them in Peking next fall. Cousteau represented the French Navy in Shanghai in the 1930s.

At one point over the weekend, Cousteau and Tim Cothren, a 29-year-old producer whom Cousteau has just hired away from ABC's "20/20," huddle over a map of the Pacific as they plan Calypso's voyage. They talk days, winds, currents.

Cothren, who will produce a two-hour travelogue on the Pacific crossing, first saw a Cousteau movie when he was 8 years old. Now he is in awe. "To be called in to brainstorm with Captain Cousteau," he says later, "is very thrilling, to say the least."

Cousteau is asked whether he isn't a little concerned about taking Calypso across the Tasman Sea, where Sir Francis Chichester capsized amid gigantic waves.

"No!" he says, as if delighted at the thought of the Tasman Sea. "That bad weather is farther south" than Calypso's proposed route.

"We'll do better than that," he goes on excitedly, pointing on the map to something very small and lonely-looking far south of New Zealand. Campbell Island, it is called.

And what in God's name is Campbell Island?

"I don't know!" Zheek exclaims with a laugh. "As soon as I don't know what it is there, I'm fascinated!" The Moon Is Full

At dinner one night in the palm court of the hotel, Cousteau tells the story of Halcyone, second daughter of the God of the Wind, who fell in love with a king. "They were in love like few people ever get in love. It was fabulous!" The king dies at sea, and Halcyone becomes a bird and kisses him, and he becomes a bird. The story trails on into the night as Cousteau savors every nuance . . .

In the end, they live happily for eternity and, because the sea must be calm for their eggs to hatch, we have come to use the term "halcyon days."

"Isn't that a beautiful story?" Cousteau asks with a radiant smile.

Then brightly, looking around, "Where is my goddam son?"

It is time to go.

Cousteau and his son, and others in their entourage who plan to sleep at a camp near the diving site, make their way down across the beach to the Zodiak. Dominique Sumian revs up the big twin 90s. Everybody gets in, settles down.

Gently at first they move away from the pier. The water shimmers in the moonlight. The mountains are savage shapes in the night sky.

The Zodiak picks up speed, clears the breakwater. Cousteau gives us a last wave, and soon they are just a spot of light far out on the dark sea.