What's the Name of That Book??? discussion

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.

Ragboy, Rats and the Surging Sea by Alan Temperley?

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...