The Mermaid of Black Conch by Monique Roffey

In 1976, David is fishing off the island of Black Conch when he comes upon a creature he doesn't expect: a mermaid by the name of Aycayia. Once a beautiful young woman, she was cursed by jealous wives to live in this form for the rest of her days. But after the mermaid is caught by American tourists, David rescues and hides her away in his home, finding that, once out of the water, she begins to transform back into a woman.

Now David must work to win Aycayia's trust while she relearns what it is to be human, navigating not only her new body but also her relationship with others on the island--a difficult task after centuries of loneliness. As David and Aycayia grow to love each other, they juggle both the joys and the dangers of life on shore. But a lingering question remains: Will the former mermaid be able to escape her curse? Taking on many points of view, this mythical adventure tells the story of one woman's return to land, her healing, and her survival.