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.