Sea Prince and the Fire Child
シリウスの伝説 (original)
In this anime classic, an undersea prince and a woman born under fire fall into a tragic love affair.
Starring Toru Furuya, Mami Koyama, Keiko Han, Michiko Nomura, Ikue Sakakibara
Watch "Sea Prince and the Fire Child" from streaming services Tubi TV, Imdb TV (Prime), Imdb TV released in 1981. It's a animation and fantasy movie, and has a rating of 7.1 out of 10 from Imdb which is usually fine for this kind of movie, and is currently available to watch for free.