The Thirteenth Year (1999)

On his thirteenth birthday, Cody discovers a shocking secret about his origins: his mother is a mermaid. As he grapples with this revelation, he begins to experience unusual physical changes, including the emergence of fins and slimy scales. Navigating the challenges of adolescence becomes even more complicated as he struggles to accept his unique identity. With the help of friends and family, Cody must embrace his heritage while figuring out how to balance his human life with the enchanting world of the sea.