The first animated film to open the Cannes festival’s Critics’ Week, In Waves is an understated marvel, its elegant hand-drawn simplicity bolstered by a strong emotional throughline. The love story it tells — spirited, tender and wrenching — begins with the clumsy meet-cute in a suburban Los Angeles high school of AJ, an introverted skateboarder, and Kristen, a gutsy surfer. They’re vivid characters brought to warm life by unfussy animation and the superb performances of Will Sharpe and Stephanie Hsu. Moving within a few short years from blushing infatuation to friendship to committed partnership, these two will weather some of life’s harshest storms.

Based on AJ Dungo’s 2019 graphic novel of the same name, In Waves is propelled by the immediacy of autobiography; its main character, AJ (Sharpe), is a visual artist whose life is transformed by Kristen (Hsu) and her love of surfing. Phuong Mai Nguyen, at the helm of her first feature, infuses every frame of the movie with a quicksilver sensory power, from the sun-kissed watercolor palette of its coastal SoCal setting to the black-and-white scenes of an imagined Hawaiian princess, whose symbolic heroism — and connection to Kristen — is more poignant each time she appears. In addition to these monochrome sequences, the main action is intercut with scenes of AJ that foreshadow a solitary interlude for a committed surfer and artist.

As the story opens, AJ is, in the words of his best friend, Francisco (Alejandro Antonio Ruiz), “aquaphobic” — a situation that Kristen wastes no time correcting, urging the shy skateboarder into the ocean and teaching him to surf. Along with her brother, Jeff (Griffin Puatu), and cousin Eon (Johnny Young), they form a tight quartet. AJ’s new friends become an especially crucial part of his life after Francisco moves away. The two boys’ awkward driveway goodbye is a key example of what the screenplay by Fanny Burdino and Samuel Doux gets so right about adolescence, as is the tantalizing suspension of time after a boy hits send on a text to the girl he can’t stop thinking about.

The characters’ athleticism speaks volumes too, from the skateboard-level action on sidewalks to the moments when AJ awakens to the physical thrills and transcendent mysteries of catching a wave. Kristen’s surfing lessons extend beyond the physical to the historical: She tells him about the legendary father of modern surfing, Duke Kahanamoku, and how the missionaries colonizing Hawaii outlawed surfing, a centuries-old part of the local culture. For the Philippine American characters at the center of the drama, cultural identity is one facet among many, not always directly illuminated; like the snippets of Tagalog spoken by Kristen’s father, it’s an organic part of the everyday whole.

Kristen and AJ’s romance follows familiar arcs from spark to spark, but the way those moments are presented can be dazzling. They share their first kiss under an exquisite inky sky, and the sight of an elated AJ skateboarding home in the rain would make Gene Kelly proud.

All the sweeping expansiveness snaps shut with a sudden health crisis for Kristen, its onset signaled with masterful concision in a middle-of-the-night calamity that leaves her helpless. It isn’t until well after Kristen has faced a life-threatening illness and an extreme medical ordeal that she and AJ make their relationship official to her parents. Every decision becomes an expression of tenacity and determination, but also an acknowledgment that things can shift in an instant. Kristen finds her way back to her natural vivacity, but the brightness burns differently. An overhead shot of the four friends together again on their boards, waiting for a wave on the sunset-pink Pacific, is a quiet stunner, packed with feeling and hard-won knowledge.

The excellent English-language cast (the festival is screening both this version and the French, which is slated for a July release in France and Belgium) features several actors doing double and triple duty as supporting and background characters. At its center, Sharpe and Hsu create a compelling and dynamic contrast as two smart people looking toward careers and ready to build a life together. A trip to New York — depicted with a vibrancy that complements the story’s West Coast settings — finds AJ and Kristen in a paradox: more committed to each other than ever before, and also lying to each other about monumental things.

In this tale of body and spirit, Nguyen (director and artist on the French series Culottées and a storyboard artist on The Ollie & Moon Show) strikes a fine balance between narrative and visual language, the imagery bolstered by musical contributions and outstanding sound work: the whoosh of the surf, the wind combing through palm fronds, the scratch of markers on a skateboard or sheet of paper.

Water is the drama’s connective tissue. With remarkable fluency, In Waves captures its various textures, trajectories and degrees of translucency, and, in a sweetly sly touch, the way it can spatter against the lens of a camera. Eventually Kristen, AJ, Jeff and Eon make their way from the Southland to a corner of the Northwest; it’s a journey into icy beauty and a kind of terror, but, no less, a headlong plunge into the balm of love. This is a movie that effortlessly marries primal poetry to the quotidian. Its aching heart understands that a full moon of brilliant perfection can illuminate one of the most painful moments of your life.