Missing:One Fairy Tale, Mermaid Involved

So when I was little, I used to google "obscure fairy tales," then go through twenty pages of results, reading everything I could find. And I found some good stuff. The problem is, ten to fifteen years later, I'm having trouble finding it again.So I am here today to ask for your help.

There is one particular fairy tale that I've been trying hard to relocate for about three years now. Here's what I remember:

• there was a princess trapped in a castle at the edge of the ocean
• she had a mermaid friend
• the mermaid really wanted the princess to hook up with her brother
• mermen are really ugly
• when the princess wasn't interested, the mermaid started flooding the palace
• there was a prince around, too
• he might have been enchanted to be a bird, possibly a blue one
• the princess might have been a painter?

If you have seen this story, please contact me via the comments.

(Seriously guys, I'm desperate. This has haunted me for the better part of a decade.)