Need help IDing early 60s animation

When I was a wee bairn, I watched a Japanese animation with a plot that my memory insists was akin to HCA’s The Little Mermaid. I know I watched it on at least two occasions, possibly more, and I have clear recollections of a young mermaid leaving the ocean to be with a young man, but the romance was doomed, and at the end, she walked into the sea, not to die, but to return sadly to her mer-world. Does anyone else remember such a film? If so, could you point me to stills or clips? Much appreciated.
Eta: I don’t recall if it was dubbed or pantomimed, but I do recall music setting the moods of each scene

Also eta: I’ve already exhausted my google-fu

You said “early 60s” and “when I was a wee bairn” but we could prolly use some more detail on when you may have seen it.

Was it in color or b&w?

Where would you have seen this in the early 1960s? On TV? Was it a movie? Was it part of a kid’s show? Was it run in it’s own time slot like The Flintstones?

Also, have you looked at the titles compiled at LibraryThing’s List Of Mermaid Movies/TV Shows/Cartoons/Anime?

It was '62-ish, on TV. I remember it in color, but it was more likely in b&w. I don’t recall it being part of something else; it might have been on a PBS station.

Eta thanks for the list, I’ll check it out

Is that a “Rule 34” site? 'Cause someone ought to point out that those things don’t have vaginas.

They probably–ick–have a cloaca.

This doesn’t fit the timeline, it came out in 1975, but their was a Japanese anime version of The Little Mermaid before Disney’s.

The only film I see from that era (there was almost nothing before 1960) is 1961’s The Orphan Brothers, which does have a mermaid. But, according to the plotline, she’s the family servant who magically transformed into a mermaid when she’s thrown from a boat, but joins the family again as their servant at the end of the film.

Here’s the trailer (skip past the old dude introducing it):

There was a TV show called Marine Boy that only had 3 episodes, broadcast in 1965. Apparently, sequels/reboots of this show were remade in 1966 (13 episodes) and then again in 1969 (78 episodes). There's no synopsis of the original version, but potentially it could have had a full story arc about the boy and a mermaid. There's a mermaid at the end of the opening for the 1969 version:
The Wikipedia also says that this was the first anime ever dubbed and released in the US.

I’m going to guess that Marine Boy is your target, though it seems like it wasn’t shown here until 1969.

I’ll check all those links out, thank you.

I doubt it was Marine Boy, which was more of an underwater techno-adventure show along the lines of Seaquest DSV or Sealab 2020. Neptina was the semi-regular magical mermaid character, but there were no other merfolk in the show.