ABANDONED. Man turns into swamp creature

[Allysha]

I remember reading this book in the early 2000s but I don't think it was a new book. I read it when I was between 10 and 12.

I can't remember if the main character was slowly turning into a swamp creature or a fish. He my have just turned into the creature at night and then back to human during the day. I think there was a love interest and he was trying to keep the creature thing a secret from her. I'm pretty sure he lived in a house boat or a cabin close to the water. I really don't remember much else about the book. I can't remember if he was cursed to turn into the creature or if it happened when he reached a certain age.

[Diana]

Does this look familiar?

[Allysha]

No, that's not it. But, thank-you for helping!

[Lobstergirl, au gratin]

Allysha, are you still looking for this or did you find it?

[Lobstergirl, au gratin]

Allysha left the group. Moving to Abandoned.