Anabelle LeMieux spent her first six years between the inlet on Tomales Bay known as Laird’s Landing, a bohemian enclave where her grandfather, the artist and fisherman Clayton Lewis, lived and worked, and Drakes Beach Café, the restaurant her grandmother, Jonne, operated by the sea.

So when her partner, filmmaker John Giacobbe, began imagining his first feature—a fevered psychodrama about love, art and the way intimacy can curdle from within—it made sense that it would involve her return to the cove of her childhood.

Over seven days in August 2023, Ms. LeMieux, Mr. Giacobbe and a skeleton crew that included her older sister, Isabelle, shot “Crusty Fouler” on a 26-foot sailboat on Tomales Bay. The film takes its title from the barnacles that crust a hull, those stubborn organisms that cling, unseen, until they become an encumbrance.

Alex and Sue, played by Mr. Giacobbe, 34, and Ms. LeMieux, 36, set out on a sailboat to escape the wreckage of their relationship. She’s a successful painter; he’s a less successful writer nursing a crisis of masculinity after his virility is called into question. From the opening scene, in which the couple hauls a boat motor down to the dock with frantic purpose, accompanied by a low, foreboding score—their idyll feels cursed.

Onboard, their world becomes a bacchanalia of alcohol, drugs and ritualistic movement. Alex and Sue veer between tenderness and cruelty, and intimacy arrives only in the form of games. He guards a notebook filled with “dark, twisted” stories he won’t let her read. She hides the aftermath of a miscarriage. Something gnaws at them, keeping each solitary and opaque, until there’s a sudden rip in their composure and their history spills out. 

 “I have these battles with you in my head, convince myself you’re out to get me,” Alex says one night as the two lie in the cabin’s narrow bed. “It makes me hate you.”

“Well, I hate you too sometimes,” Sue replies. 

In capturing the fraying of a marriage, Mr. Giacobbe’s camera alternates between two registers: a close framed intimacy and, occasionally, a hovering, prying view that creates an atmosphere of chilly detachment. 

At one point, the pair steps onto land—Laird’s Landing, renamed “Curtis Island”—and go their separate ways. Combining the necrotic with the erotic, Alex piles a mound of soft dirt, undresses and copulates with the earth. Sue smears her face with zinc like the whiteface of a mime and dabs the apples of her cheeks with menstrual blood. 

Ms. LeMieux brings torrential emotionalism to Sue that is imbued with empathy and comic timing. Mr. Giacobbe brings a pervading darkness, the ability to at once solicit and repel sympathy, menacing one instant and pitiable the next.

The couple met nearly a decade ago in an advanced improv class in Los Angeles. 

“He was so not my type,” Ms. LeMieux said. “He was straight out of Massachusetts, wearing a polo shirt, clean cut, talking about his fraternity,” she said. “But then he would perform, and he was the funniest guy in the class, and I was like maybe I could entertain some sort of romance with this guy. Now he’s California to the max.” 

They’ve been a couple for seven years and collaborators just as long. They co-starred in “A Folded Ocean,” a 13-minute Cronenbergian short in which a couple becomes gruesomely conjoined; they toured a comedy act around L.A.; they joined the city’s clowning scene. Now, as they both develop scripts, they trade drafts back and forth.  

“It’s funny because in the movie, only one of them is super successful,” Ms. LeMieux said. “And unfortunately, neither of us is successful, so maybe that helps.” 

Mr. Giacobbe wanted to make a feature for a decade but balked at Hollywood’s catechism. “I was told I needed a certain amount of money and people and that a screenplay had to be written in a certain way,” he said. “There were all these rules and regulations you had to follow.” 

So he wrote a film he could afford: two actors, one boat, one week. He storyboarded 70 flashcards with stick figures and, six months before shooting, he took Annabelle and Isabelle onto the bay to block scenes on an iPhone. “I wanted it to feel true and raw and intense,” he said. “Difficult to watch at times but saying something about what it means to be alive.” 

Isabelle, who interned for the Light while in high school, produced the film and captained her own 1960s sailboat throughout the shoot. Though she now lives in Arcata, her boat remains moored in Marshall. There were seven people aboard, and the challenge was hiding bodies and gear every time the camera pivoted. 

“I just feel so fortunate to have had a part in documenting this place and getting it indelibly captured in the film,” Isabelle said. She remembers lighting candles and kerosene lamps at night in her grandfather’s off-grid house, bathing in the outdoor clawfoot tub and listening to his stories about the Miwok who had lived there before him.

After Clayton’s death, Ms. LeMieux’s family moved to White Rock, near Vancouver. In summer, they returned for sailing camp until the family eventually resettled in Point Reyes Station. Her first taste of performance came in the Dance Palace Summer Stock. She left for boarding school in Hawaii, came back to finish high school, and went on to Bennington College, where she studied theater and biology.

Ms. LeMieux spent five years in New York’s off- and off-off-Broadway scene before realizing, one frigid winter, that she was a Californian at heart. She moved to L.A., earned an M.F.A. from the American Film Institute, and this summer premiered her thesis film at the Edinburgh Film Festival.

Her work often circles back to the mythos of her upbringing. Her first short, the darkly comic “Good Luck in the Land of Mañana,” was inspired by a real-life family scramble to Jonne’s home following her death, before her uncle could sell off Clayton’s art. 

“We had this surreal, artistic childhood,” Ms. LeMieux said. “I was definitely a little jealous of John for making a movie in West Marin first. I’ve always wanted to shoot there, but at least I got to act in it.”

The Bolinas Film Festival presents “Crusty Fouler” at 7:30 p.m. on Oct. 17   at the Dance Palace, followed by a Q&A with the cast and crew. Tickets are $20.