Peter Benchley, whose 1974 novel "Jaws" turned shark attacks into a national obsession and who later used what he called his "fish story" to help promote oceanic conservation, died yesterday morning at his home in Princeton, N.J. He was 65.

The cause was pulmonary fibrosis, a progressive scarring of the lungs, said his wife, Wendy.

Even before it was published, "Jaws," Mr. Benchley's first novel, was becoming a sensation as word trickled out of the publishing business that a blockbuster story was on the way. Movie rights were bought up, magazine articles commissioned, and the great white shark was thrust into the spotlight in a way that foreshadowed the current national obsession with "The Da Vinci Code."

For several years in the mid-1970's, the great white shark was the subject of essays and comedy skits, swimmers teased one another with the foreboding "baa-dum" theme music from the Steven Spielberg film, and lifeguards and town elders tried to assure vacationers that it was safe to go into the water.

Mr. Benchley, who even found himself enduring the wrath of Jacques Cousteau, said repeatedly in later years that he regretted making the great white shark into a villain. But he was always fascinated with the sea, having spent summers as a youth on Nantucket, and he returned there again and again for topics for his books, including "The Deep" in 1976, "The Island" in 1979 and "Beast," a 1991 thriller about a giant squid that is driven to attack humans because its natural food sources have been depleted.

He came from a home with deep literary roots, the son of the novelist Nathaniel Benchley and the grandson of Robert Benchley, the humorist and drama editor of The New Yorker and Life magazines. And his first book, a travel memoir titled "Time and a Ticket," published by Houghton Mifflin in 1964, reflected some of his upbringing as a graduate of Phillips Exeter Academy and of Harvard, where he graduated cum laude with a degree in English in 1961.

The memoir recounted a post-graduation trip around the world where the illusions of an idealistic young man are colored by the realization that what most people are searching for in an island paradise is "a place that is spoiled, a place that looks unchanged but that has — hidden among the trees — aqualungs, water skis, sailboats, movie theaters, saloons, night clubs and dance bands."

Before the memoir was published, Mr. Benchley went to work for The Washington Post, where he wrote news articles and obituaries, later moving to Newsweek. In 1967, he was hired as a speechwriter for the Johnson administration, where he befriended Tim Wirth, then a White House fellow and later a United States senator from Colorado. "Peter was a wonderfully graceful writer," Mr. Wirth said. "He was very political and really committed," something that became evident in his later life as he embraced the cause of ocean conservation.

It was while working as a freelance writer that he was invited to lunch by Tom Congdon, an editor at Doubleday, who asked if he had any ideas for a novel. In fact, he had. As he later described it, he said, "I've been thinking about a novel about a great white shark that appears off a Long Island resort and afflicts it." The idea came from a news article he had read about a fisherman who caught a 4,500-pound great white shark off Long Island in 1964. Having spent many hours fishing off Nantucket with his father, he knew of sharks, and he believed he knew how to tell a story.

Mr. Congdon agreed and acquired the right to publish the book for a small advance. Mr. Benchley wrote in a rented room over a garage in Pennington, N.J., the author John McPhee, a longtime friend, said.

"He was Robert Benchley's grandson when he was sitting in that garage," Mr. McPhee said. "He had to deal with that. But he wrote this book out of his imagination, about a shark, and that led him into a million other places, an interest in natural history, and made him into quite an expert about the subject. The cascade of money that poured upon him did not change him much from the person who was sitting in that garage."

Mr. Benchley's conservation work included serving as a spokesman for the Environmental Defense Fund and working with WildAid, traveling to teach about sharks and to try to warn against the practice of killing sharks for their fins, a delicacy especially popular in Asia.

In addition to his wife, he is survived by a brother, Nathaniel, of Manhattan; three children, Tracy Benchley Turner of Rye, N.Y.; Clayton, of Manhattan; and Christopher, a student at the University of Pennsylvania; and five grandchildren.

For their 40th wedding anniversary last year, Peter and Wendy Benchley went diving, looking for great white sharks in the Pacific Ocean off San Diego. "Many of the letters he got were from people who read 'Jaws' as a kid and were captivated by it, and who then went on to become marine biologists or who were teachers who would focus some of their time on the ocean," Wendy Benchley said. "Maybe when 'Jaws' first came out people were scared of the water. But the next generation found a great adventure story, and many of them wanted to learn about the ocean. That thrilled Peter."

Peter B Benchley