Will is a young merman still living in his parents’ basement. He is underpaid and underappreciated at his job fetching parts to make underwater vehicles. But it’s all worth it just to see Amelia. Aided by a talented team, Will has the opportunity to impress the girl. He is tasked with designing a new engine. Will turns toward a brilliant mind who has a sketchy past and a dangerous plan. They laugh, they cry, they nearly die. But in the end, Amelia saves the day.