Remembering animation but can’t find anything

I recall in my youth seeing something on TV that was a beautiful but dark The Little Mermaid by Hans Christian Andersen … particularly the imagery of the young mermaid swimming up in the very green ocean. It was NOT the 1975 Japanese version, it was something though from the 70’s or 60’s or even before and strikes me as an art style being European classic of some type and not the earlier Russian version either.

I’d know it if I saw the image. I didn’t make it up. It’s been in my mind ever since then, and I’ve never found what it was.

I’ve been over indulging in Beauty and the Beast this past week and that has brought this memory up all the more insistent that the puzzle needs to be solved, but it’s a lost cause at this rate. Really, really frustrating.