(Maybe YA) Gothic-ish Fantasy book about a man who finds a beached mermaid and keeps her captive. He makes money by selling things he finds washed up on the shore. Read in 2000's.

[Josie]

Read this book as a child (some time in the noughties) about a young man who makes money by selling things he finds washed up on the shore. He finds a mermaid and keeps her captive. Mermaid has really long nails/isn't the pretty Ariel-type. I distinctly remember her being on his couch, and there being an old man friend. I feel like the book had a weird name, something like raggedy? The cover was very dark, and in general the book was very gothic, dark and bleak.

[Becca]

Ragboy, Rats and the Surging Sea by Alan Temperley?

[Kris]

Becca's suggestion of Ragboy, Rats and the Surging Sea by Alan Temperley looks very promising.

Here's one review with more details on Goodreads - https://www.goodreads.com/review/show...