John Casey, a writer of lyric yet taut prose in novels, essays and short stories who won the National Book Award in 1989 for “Spartina,” the story of a rough-hewn fisherman that reviewers called the best American story of nautical life since Hemingway’s “The Old Man and the Sea,” died on Feb. 22 at his home in Charlottesville, Va. He was 86.

His daughters Clare and Julie Casey said the cause was complications of dementia.

Mr. Casey, who spent most of his literary career as a professor of creative writing at the University of Virginia, was best known for his pinpoint renderings of blue-collar characters, like Dick Pierce, the Rhode Island boatman at the center of “Spartina,” whom the author referred to as a “swamp Yankee.”

The novel revolves around both Pierce’s romantic entanglements — long married, he starts an affair and gets his lover pregnant — and his struggles to build a boat. Spartina, a sea grass, becomes the unifying metaphor of the book.

“Only the spartinas thrived in the salt flood, shut themselves against the salt but drank the water,” Mr. Casey wrote. “Smart grass. If he ever got his big boat built he might just call her Spartina, though he ought to call her after his wife.”

The novelist Susan Kenney, writing in The New York Times Book Review, called the novel “splendidly conceived, flawlessly rendered and totally absorbing.”

Mr. Casey’s National Book Award win was something of a surprise, beating out heavy hitters like “The Joy Luck Club” by Amy Tan and “Billy Bathgate” by E.L. Doctorow.

“Thank goodness these five judges were in the mood,” he said at the awards ceremony. “Because that’s what it is, they were in the mood for my book.”

“Spartina” was Mr. Casey’s third book, following a novel, “An American Romance” (1977) and a book of stories, “Testimony and Demeanor” (1979). He also wrote magazine essays about his love for the outdoor life, especially running and rowing.

“John was a charismatic raconteur who knew something about everything and everything about some things, particularly writing,” the actor and playwright Eric Bogosian, a close friend, said in an email. “I considered him a mentor.”

John Dudley Casey was born on Jan. 18, 1939, in Worchester, Mass., where his father, Joseph, was a lawyer and a Democratic U.S. representative. His mother, Constance (Dudley) Casey, was a Democratic Party activist.

John grew up mostly in Washington, D.C., though he spent a year at Institut Le Rosey, a boarding school in Switzerland.

Intent on following his parents into public service, he studied Russian history and literature at Harvard. After he flunked out in his junior year, his father made him join the Army Reserve. He returned to Harvard and graduated in 1962, then from its law school in 1965.

While in law school, he took a writing course with Peter Taylor, a novelist and short story writer, who saw promise in his work and encouraged him to pursue fiction.

After practicing law for a year, Mr. Casey decided to follow Mr. Taylor’s advice. He received a fellowship to the Iowa Writers’ Workshop and completed his master’s degree in 1968.

Among his classmates were Gail Godwin and John Irving, and he found a close mentor and friend in Kurt Vonnegut, an instructor at the workshop.

Despite Mr. Casey’s elite background, his friends said they could already see in him the writer he would become.

“I can’t explain it, but — even in Iowa — there was something of the solitary, intrepid mariner about Casey,” Mr. Irving wrote in an email.

Before graduating, Mr. Casey sold two stories to The New Yorker and another to Sports Illustrated.

Rather than march triumphant into a literary hot spot like New York or Cambridge, Mass., he and his wife, Jane, whom he had married in 1967, bought land on an island in Narragansett Bay, in Rhode Island, where they lived without electricity or phone service.

He and his wife later divorced. He married Rosamond Pittman in 1982; they also later divorced. He married Robin Fray in 2012. She died in 2015.

Along with his daughters Clare and Julia, from his second marriage, he is survived by two daughters from his first marriage, Nell and Maud Casey; his sisters, Constance and Caroline Casey; a brother, Joe; and two grandchildren.

Mr. Casey moved to the University of Virginia in 1972 at the behest of Mr. Taylor, who was teaching there and wanted to build out its creative writing program.

He developed a reputation for generosity with his time and talents, encouraging even non-students to submit writing for him to critique.

“If someone in the community showed up with a Chapter 1 that showed any promise, John would read it,” the novelist Ann Beattie, who taught alongside Mr. Casey, said in an interview.

Among his early students was Breece D’J Pancake, a promising writer from West Virginia. Mr. Pancake, who almost immediately established himself as a rising literary star, published several stories in The Atlantic before dying by suicide in 1979.

His death hit Mr. Casey hard. In 1983, he edited “The Stories of Breece D’J Pancake” and wrote an afterword.

Mr. Casey published three more books of fiction after “Spartina,” a collection of his outdoor writing, a book about the art of fiction and two translations of novels originally written in Italian, which he had learned while in Rome on a fellowship.

He continued to teach at Virginia until retiring in 2018. But he departed under a cloud.

In 2017, several former students filed separate Title IX complaints against Mr. Casey, accusing him of sexual harassment, inappropriate touching and favoring male students in his classes. A university panel recommended he be dismissed, but he retired instead.