The youngest of Queen Tethys (Cate Blanchett)'s sons, Aaron (Shawn Mendes) is a handsome and charming young merman with a thirst for adventure. Longing to find out more about the world beyond the sea. Aaron visits the surface and falls into the beautiful Princess Emily (Rachel Zegler). Following his heart, he makes a deal with the evil sea sorcerer, Ursus (Benedict Cumberbatch), to experience life on land.
