I'm not quite sure how the song got onto one of my ancient audiotapes, but I've remembered the refrain from Tomoko Tane's（種ともこ） "Mermaid In Blue" although I didn't know that it was the theme for the anime, "Sangosho Densetsu -- Aoi Umi no Elfie"（サンゴ礁伝説～青い海のエルフィ...Coral Reef Legend -- Elfie of the Blue Sea） back in the mid-80s. From what I've seen of the excerpt above, those submariners must have had a grand time on those adaptable jet-skis.
Tane released her song as her 2nd single from May 1986, and even without the anime knowledge, I immediately got this image of a fantastical underwater kingdom just from her vocals and the melody. "Mermaid In Blue" just has that sparkling quality about it, and reading the other articles of her songs by nikala pretty much cemented my impression that Tane is quite a unique pop singer. Usually when I go and see a movie, it's to escape for a few hours. This song also has that escapist quality....perhaps it's just for 4 minutes, but often that is enough to get into a nice headspace.