Fifty years ago, when Wendy Benchley’s late husband Peter Benchley wrote a novel called Jaws, neither had any idea that it would become a phenomenon.

No one was talking about sharks back then. A 20-something, shaggy-haired Stephen Spielberg was still unknown. And the idea of adapting a shark story for the screen seemed logistically challenging at best and delusional at worst.

“When Peter was writing the book, and when it was published, we had no anticipation it would ever be a movie because who could ever train a great white shark?” Ms. Benchley said.

The book by Mr. Benchley was published in February of 1974 and the film rights were quickly secured. Mr. Benchley wrote the screenplay, also credited to Carl Gottlieb, and in May of 1974 filming began on Martha’s Vineyard. The crew was largely made up of Islanders working hard behind the scenes.

Half a century later, the film’s impact endures. Jaws spawned multiple sequels and an entire “sharksploitation” genre of cinema. The movie is baked deep into Island lore, with tourists flocking year-round to filming locations and “Amity Island” apparel decorating the windows of T-shirt shops on every corner.

Sharks entered the zeitgeist after Jaws, on the Island and around the world.

“I think that Jaws did strike a chord,” Ms. Benchley said. “How do people cope with a menace they can’t control?”

Peter and Wendy Benchley cage diving with a great white shark. — Courtesy Wendy Benchley

On Tuesday, August 6, Ms. Benchley will give a talk about her experience with the book and the film at the Katharine Cornell Theatre, hosted by the Vineyard Haven Library. She will also give a talk at the Edgartown Library on August 8.

To Ms. Benchley, the public fascination with the film, and by extension sharks, had positive and negative reverberations. She said it inspired people to begin studying sharks and that the field of marine research is better for it.

“Peter received thousands of letters from people all over the world saying, ‘Jaws made me fascinated with sharks and really made me want to study more about them and understand more about the ocean,’” she said. “Many people said, ‘I really want to be Hooper.’”

But there were also tragic consequences. The film’s images of sharks being slain to great fanfare stirred a widespread cultural desire to hunt the animals for sport.

Ms. Benchley said she abhors the practice as cheap machismo, disguised as a noble quest for vengeance. She remembers a reporter calling her husband from a bar where a man was boasting about shooting and killing a group of sharks feeding on a whale carcass.

“He thought he had done a wonderful thing and he dragged one back so that people could see,” she said. “So Peter said, ‘Will you please tell the man right now at the bar that that’s about as courageous as going out into your backyard and killing your dog with a rifle?’”

Shooting Jaws in Edgartown in 1974. — Edith Blake

The Benchleys were so disturbed by what they witnessed in the wake of Jaws that they felt a personal responsibility to advocate for sharks and their habitat.

Ms. Benchley served on the board of the Environmental Defense Fund (EDF) for 18 years, and Mr. Benchley became the longtime spokesman for the EDF. But Ms. Benchley said she was his “policy wonk,” often standing in to answer difficult questions in his stead.

She also headed an ambitious campaign with WildAid to stop shark finning. Though shark fin soup is a delicacy in many places, finning a shark means it will die a slow death, either from blood loss or suffocation.

After about a decade of campaigning against it, consumption of shark fin began to decrease.

“The Chinese government stopped serving it at their government functions, the hotels stopped serving it, the airlines stopped serving it,” she said. “The demand for shark fin soup went down by 80 per cent.”

Ms. Benchley’s love for sharks has continued to grow in the years since Jaws. She was elected to the Women Divers Hall of Fame for her numerous diving expeditions where she’s had thrilling encounters with sharks.

When Mr. Benchley asked her how she wanted to celebrate their 40th wedding anniversary, she chose cage diving off the coast of Guadalupe Island where female great whites congregate every October.

“They’re the big ones ­— they’re beautiful, big, round, torpedo shaped, gorgeous, great white sharks,” she said. ​​”You could reach out and stroke them. If you stroke it from head to tail it’s smooth like a leather glove. But if you go the other way, the denticles that are in the skin catch your hand.”

Though the cultural impact of Jaws is complicated, the unlikely film fostered in Ms. Benchley an abiding sense of duty ­— to sharks, the environment and the entire marine world.

“It’s their ocean,” she said. “They’re just doing what all animals do, including us.”

An Evening With Wendy Benchley, hosted by the Vineyard Haven Library, takes place Tuesday, August 6, beginning at 6 p.m. at the Katharine Cornell Theatre, 51 Spring street, Vineyard Haven. She will also give a talk at the Edgartown Library on August 8 at 6 p.m.