Magnus Fin and the Selkie Secret

Magnus Fin discovers his unique heritage as a half-selkie on his eleventh birthday, which allows him to breathe underwater. When a mysterious chest washes ashore, he is drawn to it but injures himself, revealing his selkie nature and attracting attention from his teacher and peers. Meanwhile, Neptune, the sea god, faces his own crisis with stolen treasures affecting his powers. As Magnus embarks on a quest to uncover the chest's secrets and restore balance, he must also protect his family's selkie identity from a journalist's investigation. This is the third installment in the series.