Looking for books with similar themes/tropes to the little mermaid

The littler mermaid was my favorite movie as a kid….. and still is. I’ve looked at retellings but they’re more on the fantasy side instead of the modern/fan fiction side.

I think I like the trope of falling in love, being separated, and then fighting for that love again. The more dramatic reunion the better.

Does anyone have any recommendations or must read that fit a similar trope or plot? Doesn’t need to actually include mermaids.