The actress and stunt woman Susan Backlinie, whose portrayal of a violent death as the first shark attack victim in the opening scene of the blockbuster movie “Jaws” terrified moviegoers, died on Saturday. She was 77.

Ms. Backlinie died at her home in California, her agent, Sean Clark, said on Sunday. He said she had a heart attack.

“Jaws,” the 1975 movie directed by Steven Spielberg, memorably features Ms. Backlinie in a scene in which she played a skinny-dipper, Chrissie Watkins, who runs along the beach and dives into the water for a nighttime swim.

The placid scene is shattered as she is suddenly pulled under the water. She screams while being violently thrashed by an unseen great white shark and tries desperately to cling to a clanging buoy only to be pulled below the water one final time.

For the scene, Ms. Backlinie was secured to a harness, according to The Daily Jaws, a website devoted to “the phenomenon, history, legacy and craft” of “Jaws.” The Palm Beach Post reported that Ms. Backlinie was wearing a pair of jeans with metal plates stitched into the sides with cables attached.

“To create the effect of being pulled through the water, Susan was tethered to a line anchored to the ocean floor beneath her and deliberately left unaware of when she would be submerged initially, aiming to elicit a more authentic surprise from her,” The Daily Jaws reported.

In an interview with The Post in 2017, Ms. Backlinie recalled Mr. Spielberg telling her, “When your scene is done, I want everyone under the seats with the popcorn and bubble gum.”

She said, “I think we did that.”

In “Jaws: The Inside Story” documentary, Mr. Spielberg described the sequence as “one of the most dangerous” stunts.

“She was actually being tugged left and right by 10 men on one rope and 10 men on the other back to the shore, and that’s what caused her to move like that,” he said.

The actor Richard Dreyfuss, who starred in the movie as the oceanographer Matt Hooper, explained in the documentary how Ms. Backlinie and Mr. Spielberg added to the terror of the scene by later recording her screams.

Mr. Spielberg “had her tilt her head back and he poured water down her throat while she screamed, which is now known as waterboarding,” Mr. Dreyfuss said.

Ms. Backlinie worked with Mr. Spielberg again in the 1979 parody war film “1941” in which she spoofed her “Jaws” character by taking a late-night swim. As the suspenseful score from “Jaws” played, she encountered the rising periscope of a Japanese submarine instead of a shark.

Susan Backlinie was born on Sept. 1, 1946. At age 10, when she was living in West Palm Beach, Fla., she swam for miles off the coast and in local pools, The Post reported. In high school, she was a cheerleader and a state freestyle swimming champ.

She performed as a mermaid at Weeki Wachee Springs State Park, a tourist attraction on Florida’s west coast, and eventually moved to California.

Ms. Backlinie is survived by her husband, Harvey Swindall, according to Mr. Clark.

After “Jaws,” she continued to work in films, appearing in the horror movie “Day of the Animals” (1977), and as a water ballet performer in Jim Henson’s “The Great Muppet Caper” (1981). She also appeared in an episode of the stunt television series “The Fall Guy” in 1982.

But it was the opening scene of “Jaws” for which she would be best remembered.

In the interview with The Post, she recalled how fans who attended movie conventions talked to her about their fear of swimming because of that scene.

“One of the main comments I get from everybody is, ‘You know you kept me out of the water,’” she said.