My Teenage Life Underwater

My Teenage Life Underwater (私の水中十代の生活) is a 2002 Anime Atrocities short film directed by Kagami Ochiai and produced by Drillimation Studios. The film was released on VidSpace on June 21, 2002. The film chronicles the life of a Japanese-Canadian girl in Nova Scotia named Mizuki Umino facing new life challenges when a spell causes her to permanently transform into a mermaid on her 13th birthday.

Plot
In Halifax, Nova Scotia, Canada, a Japanese couple is blessed with joy with the birth of their daughter Mizuki Umino. A few years later, Mizuki's younger sister, Youko Umino, is born. Mizuki happily enjoys her life with her sister until her parents learn of a prophecy that their eldest daughter Mizuki will permanently become a mermaid on midnight the day she turns 13.

Eventually, that day comes and on the night before her 13th birthday, her parents give her one solemn farewell before they witness the transformation as Mizuki begins her new life in the Atlantic Ocean.