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 …