The Returning Mermaid

[Various]

Years ago, something came from the sea. She stayed for a week, during the time of the year she had legs to walk on land before returning to the depths. She returned each year, for four more years, before she stopped coming back. Now, she has returned. Decades have passed but age has not touched her. If her human partner has seemingly moved on, all the better. Of course, it's strange that they always insist on oceanfront property when they move.

Depending on the preferences of the partner, I see the mermaid either as being very talkative, but evasive about why she left for so long, or incapable of telling her partner because what sounds she does make are decidedly oceanic.

The mermaid problem:
Although she'll be human enough during some of the story, the mermaid may return to her true form. Which leads to the question of what exactly that is.
• She's fish-like. That is traditional. This makes things a bit tricky, although she could be the Starbucks-type.
• She's dolphin-like. In this form, she's a mammal. This would do a LITTLE bit to explain away the upper half.
• She's squid-like. She's a bundle of tentacles below.
• She's jellyfish-like. Safe sex takes on a whole new meaning.

PM if interested.