He was not the first fair-haired son of Southern California to dream about spending his life in (or near) the ocean. But as the others grew up and became dentists, insurance salesmen and truck drivers -- or failed to grow up, and became career beach bums and family embarrassments -- Robert Ballard stayed true to the cause. And the result, at 39, is handsome proof that childhood dreams sometimes come true, and that the child may, after all, know what is best for the man.

What Ballard does for a living is to probe the bottom of the sea -- specifically the 40,000-mile-long Mid-Ocean Ridge, a range of mountains bigger than the Rockies, Andes and Himalayas combined, which, as he says, "goes all the way around the world like the seam in a baseball."

If you're interested in getting away from it all, and in having stories to tell upon your return, here is a site worthy of your consideration. There is, as yet, no "Mid-Ocean Ridge" exit off the Beltway, and you can't book a package tour through your local travel agent. But to hear Ballard tell it, this is a case where exhilarating adventure -- the stuff of TV specials, National Geographic articles and boyhood fantasies -- goes hand-in-hand with good hard science. By sticking his nose down into the bottom of the ocean, man, in Ballard's view, has confirmed and considerably refined a once-daring theory about how the world is put together and how its most dramatic features -- continents, mountains, mineral deposits and, conceivably, life itself -- came to be.

There are doubters. There are still a few who question the idea of "plate tectonics," which sees the Earth's crust as a great jigsaw puzzle of 12 major pieces floating on an intensely active semi-molten interior; and there are more than a few who question the value of studying the Earth's structure in a cute little submarine named "Alvin."

But today's doubts are nothing compared to the ones that used to greet these propositions. Ballard was a doubter himself when, as a 25-year-old navy oceanographer assigned to the Woods Hole Oceanographic Institution on Cape Cod, he heard a lecture on plate tectonics by M.I.T.'s Patrick Hurley. "It seemed outlandish to me -- it seemed bizarre to me that the continents were moving," he says. Yet not long afterward, in his doctoral dissertation, he sought to explain the present shape of New England and its offshore regions in terms of the shifting movements of the American, African and European plates a few hundred odd million years ago.

It wasn't until 1960 that geologists took stock of the Mid-Ocean Ridge in its awesome entirety, and it wasn't until 1972 that anyone suggested using submarines to inspect it first-hand. Even now, after an eight-year series of international expeditions, less than one-tenth of one percent of the ridge has been visited by human beings. But that relatively marginal encounter, from the ridge's point of view, has added up to a total infatuation, from Ballard's.

"For the last decade it's just been a roller coaster ride, and I'm wondering when it's going to slow down," says Ballard, a lean and sandy-haired scientist who calculates that he has been on more dives, seen more of the ridge, and spent more time doing it than anyone else in the world.

The work has produced its moments of suspense, like the time the Alvin got stuck in a crevasse for several hours, and its stunning surprises, like a network of ocean-bottom hot springs and a new community of animals basking in the surrounding warmth. But a trip to the bottom of the ocean is not all high drama, to hear Ballard tell it. It takes two hours to reach the typical site and two hours to return, and "when you get done with a dive, you are beat, you've got a headache that won't quit, you're exhausted."

Which is why he looks forward to the time when remote cameras and robotics will let scientists forage in the ocean deeps without actually going there. With a new system called Argo-Jason (so named, Ballard wryly insists, because "I thought we'd go for the Golden Fleece award right off the top"), "you can create topside the illusion of being down at the bottom. You can have someone sitting at a screen operating a manipulator and he'll have the sensation of being 20,000 feet down." Argo-Jason will be a way to "separate one's psyche from one's body." It will be "an R2D2 that will house our mind." In the meantime, Ballard has been filling a similar function for the non-oceanagraphic community, making two or three trips a year to exotic sections of sea bottom, then surfacing to draw "oohs" and "aahs" from ground-bound audiences of the curious and the influential.

Audio-visual aids help make his subject matter come alive, but the most important ingredient in Ballard's presentations is his large store of natural effervescence and the aquatic equivalent of Tom Wolfe's "right stuff." This is a man who can get excited enough about a new technological advance to assure listeners that it will "knock your socks off." Yet he is ultra-sensitive to the hazards of being seen, by his colleagues, as a glory-seeker, a popularizer or, in short, Carl Sagan with gills.

In addition to his speaking engagements, Ballard has written or co-written magazine articles, has made a TV special (with a second on the way), is negotiating with Walt Disney World about its possible use of ocean-bottom video transmissions, and has a book on plate tectonics (to be called "Exploring Our Living Planet") in the pipeline. He also has an eye aimed over his shoulder at suspicious folks like the Woods Hole colleague who, passing Ballard in a corridor, sarcastically remarked: "Well, I finally understand what you're doing. I read about it in National Geographic."

By trying to communicate beyond the usual scientific circles, "you set yourself up for cheap shots that you can't do much about," says Ballard. "I draw a lot of criticism for popularizing science." Popularizing is a genuinely hazardous business, he adds, because the press tends to oversimplify and to glorify the role of the individual in what is essentially a group endeavor. If a scientist cooperates with an article or program that contains such distortions, "the scientific community doesn't forget," he says. "They say, 'This guy is being a glory hound.' So you've got to be careful."

His own way of being careful is to emphasize the contributions of others and the theory that "the discovery of truth is inevitable. It's just a question of whether an individual or a group of individuals will make it happen faster." Most of the scientists and technicians who have taken part in the ridge expeditions are people who "work for nothing" and "whose total motivation has zero to do with money," according to Ballard. "It's fascinating," he adds, "to have raw talent in such concentrations." Fascinating, that is, from the psychological as well as the intellectual perspective: "You trap a person who can't leave you. You master them. You find out what they're made of."

In January 1972, the National Academy of Sciences sponsored a get-together of international earth scientists at Princeton, to discuss how to proceed with the exploration of the Mid-Atlantic Ridge. Submarines were the one way a clear majority of those present did not intend to proceed. "There were quite a few people -- particularly the geophysicists, who were the creators of plate tectonics and were somewhat highbrow," says Ballard, "who felt that submarines were expensive toys that geologists played with, and that no real good science would come out of them." Hence it was a stressful assignment for "the only one at the whole meeting who didn't have a doctorate" (at the time) to be called on to make the contrary argument.

"So I went into the pit and gave my presentation," he says, recalling a pivotal moment in his life. And when he had finished, a prestigious skeptic from M.I.T. rose "almost like a senator in Rome," according to Ballard, "and said, 'Would you please give a single example of a significant bit of science that has been done from a manned submersible?' "

"I was speechless," he says. "Fortunately, a scientist named Bruce Luyendyk rose and said it was not the fault of the technology that nothing significant had ever been done with it. It was the fault of science that it had never tried."

And so Project Famous was born. The acronym stood for French-American Mid-Ocean Undersea Study, and it culminated in the summer of 1974 with four ships and three submarines (including the Alvin) crisscrossing a section of the Mid-Atlantic Ridge southwest of the Azores -- mapping, collecting samples and snapping pictures. The location was chosen as typical of the ridge, and it proved to be the site of almost continual micro-earthquakes, a network of cracks on the ocean floor, an abundance of fresh lava formations and assorted other signs that the Famous team had, indeed, alighted on the boundary between two great continental plates, a boundary where new crust was being formed to fill the gap left as the plates continued to separate.

When plates move apart, "the Earth responds by sending some of its plastic interior up into the tear or wound," Ballard explains. "Some of this magma flows out onto the sea floor, where it cools rapidly and coagulates, forming volcanic pillow lavas. The remainder, called plutonic rock, solidifies deep in the rift between the plates, much as household cement may harden in the neck of an opened container." Then the moving plates cart the surface rock away from the volcanic ridge in a process Ballard describes as a "geological conveyor belt," producing an essentially horizontal rather than vertical series of chronological layers.

Off the Azores, the plates were separating at a rate of about an inch a year, and the geological activity was correspondingly slow. (Ballard likes to compare the human perspective on plate movement to the butterfly perspective on the growth of a redwood: "If you ask that butterfly if it perceives that tree it's sitting on as alive, it will say, 'Of course not. I've been here all my life and it hasn't done a thing.' ") In 1979, Ballard was one of the leaders of a U.S. expedition to the vicinity of the Galapagos Islands in the Pacific, where the plates were moving faster -- about three inches a year. Using a sonar-guided, ship-towed camera sled called Angus, which Ballard helped design, the Galapagos team found and photographed extraordinary hot springs where sea water and molten material were interacting deep in the cracks that lined the ocean floor. The team also found, quite unexpectedly, life -- giant clams, crabs, tube worms and other animals in sunless depths far below the ocean's usual population centers.

Regrettably, there were no biologists along for the ride. Ballard had invited a few, but they turned him down, figuring they wouldn't see anything worth their while. "And all I can say is they made a hell of a mistake," he says. In '79, the team returned to the Galapagos, equipped not only with biologists but with a National Geographic film crew and a new lighting system allowing the three-ton Angus to skim through the waters 30 to 40 feet above the bottom, identifying photogenic locations to be filmed with greater care from the Alvin. (The resulting program, called "Dive to the Edge of Creation," was aired in January 1980, and "the Fonz outdrew us four to one," Ballard laments.)

Even more striking pictures of the ridge were shot later that year, off the tip of Baja California. When Ballard showed some of this footage at an Audubon Society lecture in Washington this spring, the audience was riveted by the sight of 10- and 20-foot tall natural chimneys belching forth pewter-gray smoke, and little white crabs darting into the smoke, then darting out again as they began to be singed by the heat (so intense that it melted the Alvin's thermometer and would have done the same for the Alvin's portholes had the sub strayed too close).

But the Baja discoveries were more than audience-pleasing. Here, with the help of sulfide-eating bacteria, a whole community of organisms (including a 10-inch-long fish christened the "21-degree north vent fish") fed on effluents pouring from the Earth's interior. A new chain of life had been discovered, and because it seemed to get by without sunlight, while exploiting a poisonous chemical environment similar to that which may have preceded the first photosynthesis, some scientists now think they have identified a rough model for the creation of life on Earth. "It's conceivable," says Ballard, "and some are now suggesting -- although I'm not one of them, because I'm not a biologist -- that life may have formed in similar vents, but in shallow water."

Ballard is suggesting, as a geologist, that the chimneys found at 21-degrees north are "a natural factory generating heavy metals," and that some of the world's key mineral deposits may have been created in this fashion. Cumulatively, the visits to the ridge are a "detective story," he says, in which "you put together a series of clues and a pattern starts to evolve." After 10 years, "we have just now developed a model to explain where hydro-thermal vents are, and where they aren't, and why." Beyond its insights into the basic structure of the Earth, the work has yielded spinoff developments in deep-water submarine construction, in underwater photography, in ocean-bottom mapping technology, and in remote-controlled "imaging" systems like Argo-Jason.

Despite his general exuberance, Ballard is dubious about the immediate prospects for deep-sea mining, because "we have found little deposits all over the place, but not huge ones." Just the same, he questions the United States' rejection of the Law of the Sea Treaty. Other countries resent it, he says, and their resentment tends to focus on U.S. oceanographers. Finances permitting, the Alvin's next major voyage will take it to an area of the East Pacific Rise that is in international waters -- partly because of what Ballard calls "unreasonable demands" concerning further exploration of the Galapagos Rift, and there have been clearance problems with Mexico as well. "It's getting tougher and tougher getting permission," he says.

Despite the low staff salaries, the work is hugely expensive. A typical expedition lasts a month or so, involves several vessels and as many as 200 participants, and carries a total price tag of $750,000 or more. It's like a New York City cab ride "and the meter is tick-tick-ticking away," says Ballard. As a result, he spends an estimated quarter of his time raising money, which entails extensive dealings with the National Science Foundation as well as private sources, and an ongoing effort to satisfy the "what-have-you-done-for-me-lately?" mentality that holds sway over the funding of scientific research.

"You're being required to do science on a scale of one year, which is very difficult to do," he says. But this is one government dependent who isn't making dire predictions about a cutoff in funds. Whatever else happens, Ballard predicts, the exploration of the Mid-Ocean Ridge will continue -- because "it's too good."