His best-selling second book, "Jaws," is still being read in 30 languages, still being shown in film version at a smattering of movie houses, still keeping the impressionable away from beaches for fear of imagined shark attacks, still making money. Novelist Peter Benchley is just as confounded as anyone by its continuing success, but he's learning to live with the consequences.

He has, for instance, become moviewise. Now he knows the difference between personally having net points (percentage) and adjusted gross points in a motion picture. When he talks about the star of the film version of his latest book. "The Deep," he wonders aloud if actor Nick Nolte's "Rich Man, Poor Man" television fame will "translate itself into box office." He can even shake his head with knowledgeable despair over the lack of box office John Frankenheimer's new movie is doing in L.A.

Benchley is also learning how to day no to national magazines that want to take photographs of his swimming pool, because the privacy his wife, Wendy, feared would be relinquished with the sale of "Jaws" is perilously close to being lost.

On the other hand, the 37-year-old Benchley is comfortable with the physical and psychological comforts of success. It was afforded him a writer's luxury - time - and predictable accountrements - a tennis court and an enlarged kitchen for his 67-year-old Princeton home.

And the selling power of "The Deep," a page-turner about a couple who find a fortune in morphine ampules while diving off the shores of Bermuda, has eased the pressure that built for him to follow "Jaws" with another best-seller.

Waht Benchley has to resist these days is the enticement to sit back and enjoy it all.

So far, he seems to be resisting. although the attraction he has for invitations to appear on outdoorsmen television shows is an indulgence he allows himself. (He's gone treasure diving off Bermuda with Beau Bridges and shark hunting in Australia with Princetonian cameraman Stan Waterman.) Playing bit parts in movies made from his novels is another. (He was a TV commentator in "Jaws"; his role as a ship's mate in "The Deep" is on the cutting room floor.)

His self-imposed disciplines include daily writing sessions with Newsweek book critic Paul Zimmerman, with whom he's co-authored a satire called "The Most Powerful Man in the World." The screenplay, now in its third draft, has attracted director Alan J. Pakula and United Artists.

Benchley's doctor has imposed sterner restrictions resulting from the removal of three vertebrae and the fusion of the discs in his back. The therapy includes swimming laps at a neighbor's pool (his own is too small) but tennis has been taboo since Nov. 30. Benchley, a tennis addict, remembers the date.

His light brown hair is noticeably grayer and he's had to hire a second accountant to wrestle with Universal Pictures over his share of the movie, "Jaws," but the Benchley humor is amiably intact whether he uses it while swatting a giant been in his house or in mimicking a customs official who gave him a hard time. And there's a boyishness about his attachment to things "Jaws"-related that transcends whim or pride. It manifested itself in a collection of shark memorabilia - the serated teeth that line a bookcase in his writing room, the color photographs from "The Deep" and "Jaws" on the kitchen walls, the Richard Ellis oil in the living room, the upstairs hallways decorated with snapshots of marzipan sharks and bathroom monsters spawned by the imaginations of fans.

"Kids made 'Jaws' a hit movie. People who don't read books made the novel a best-seller," he feels. "But nobody had any idea that 'Jaws" would do the kind of business it did. What do the kind of business it did. What you can't predict is phenomenon and 'Jaws' was a phenomenon."

Benchley has no idea if the movie of "The Deep" will make it big. He cautiously points out that action movies like "Black Sunday" and the luckless "Lucky Lady" haven't been cleaning up at the box office.

"The Deep," filmed in Bermuda, the Virgin Islands and Australia, centers on a married couple whose scuba diving off the shores of Bermuda entangles them with murderous Bermudian drug dealers as they are forced to probe the ocean for a fortune in morphine ampules.

"The Bermuda government thought the book was unfair to blacks, politicians and the governmnet," says Benchley, "but the people loved it. They're also not too happy about having people know that there are about 300 ships sunk off Bermuda's coast and some of them carried ampules of morphine."

Benchley had a brush with customs when he tried to bring a few of those capsules back to the U.S. last summer. He had salvaged the vials from the wreck of the Constellation, a ship wellknown to Bermuda divers.

"I got busted," he remembers, going into an imitation of the customs man. "I told them the morphine inside was dead, that it had been under water, but they tested it and it turned the test fluid black. It was pure morphine. I was arrested and it was in all the local papers. They even body-searched the crew of 'The Deep when they came back too."

There was no real hassle. Benchley was released at the airport.

Benchley shares screenwriting credit for "The Deep" with Tracy Keenan Wynn and claims to have no ego about having a co-author with him.

"I did the screenplay twice," he explains. "But I was working with people who only knew what they didn't like and not what they wanted. That's when Wynn came in. Then it bounced back and forth between me and (actor Robert) Shaw."

The author says he is not even sure how "The Deep" will end when it gets to movie houses, since director Peter Yates filmed it two ways. Benchley's happy to see ti getting made at all.

"Twentieth Century Fox-turned it down," he says of "The Deep." "Universal (which released 'Jaws') turned it down too. Universal thought it would be too expensive to make. Fox had just done 'Lucky Lady' and didn't want to do another water movie and Zanuck and Brown were too busy. Columbia was the only studio willing to invest what it would take to make 'The Deep.'"

The film stars Nick Nolte of "Rich Man, Poor Man" fame as the husband, Robert Shaw as the salty diving pro who helps him fight the drug dealers and Lou Gossett as the Bermudian drug baron. At the Benchley household, the consensus had been to cast Lindsay Wagner in the female lead, but the Bionic Woman lost out to Jacqueline Bisset.

Off and on over the seven years before the publication of "The Deep," Benchley had been using his trips to Bermuda to absorb facts about sunken ships, islanders and diving.

Some 190,000 hardcovers of the book have sold and, on April 6, bookstores were bombarded with 1.2 million paperback versions of the same. Benchley estimates that if he hadn't finished writing "The Deep" "reasonably quickly" after "Jaws," the pressure to better his success would have been tremendous. Now, when he writes, he says he does not consciously consider the movie possibilites of the material, although "Jaws," with $195 million in worldwide film rentals, has become the biggest moneymaking movie of all time.

He has no connection or concern with the sequel to "Jaws," which is being filmed without his participation. He looks at it as another aspect of the mushrooming effect of its popularity.

The enormity of "Jaws'" success has left Benchley unsure of the number of copies it has sold and he refuses to be specific about how much it has earned him, except to say that it has made him rich.

Someone once asked Benchley's novelist father, Nathaniel, if he envied his son's success and the elder Benchley replied, "Envious? Are you kidding? Who'd like to live up to that act?"

The younger Benchley appreciates the sentiment. His wife has been handling the notoriety "very sensitively" and Benchley; who is friendly by nature, is beginning to hold his tongue when the questions get too personal.

A natural questions arises about the similarity between Benchley's personality and that of the male character in "The Deep," a Wall Street "customer's man" named David Sanders. Sanders is a man who went to a Jacques Cousteau lecture as a junior in college and knew by the end of the evening that "Cousteau's was the life he wanted to live." He worked at the National Geographic, thought about becoming a speech writer for JFK and dreamed of "exotic assignments" that would envelop his interest in scuba diving and killer whales.

"He's not at all like me personally," says Benchley, who wrote speeches for LBJ, contributed to the National Geographic and has an abiding interest in scuba diving and killer whales. "He's more like me in that he finds a way to do things rather than just looking at them. Most of the people I've known both here and in Washington lead, if I may borrow a Thoreauvian phrase, 'lives of quiet desperation.'"