Found: Ages 8-13, Girl goes out in a boat on her own

Found this book in a school library about a decade ago, I think it was fairly popular, I seem to remember reshelving it often. It was probably new-ish at the time, maybe 2010 or so publication date? I can see the cover so clearly, it was very simplistic and almost cartoony, mostly blue with a seagull sitting on the bow of a small rowboat, as the viewer was sitting in the rowboat looking down at the water. I think the title was just one or two words.

The main character was a girl, probably somewhere around 8-13, and her mother was gone. I think she was dead or missing, possibly on a long term work trip, but the main character seemed to think she was a mermaid or something? It was either realistic fiction or possibly magical realism; no one else thought her mother was a mermaid.

One night (maybe multiple nights?) she goes out in a little boat on the ocean (or I guess it could have been a lake). I seem to remember she lived in a fishing town, and she knew a lot about sailing, tying knots, etc but was still too young to be sneaking on the water. I think the book took place in England, but it could have been America, Canada, I'm not sure. It was definitely in English but then I suppose it could have been translated as well. I think the bird on the cover was important, maybe she thought it was guiding her to her mother?

I have no idea how it ends, I can't remember if I even read this book or just the blurb on the back cover, but I thought I had a copy and it turned out to be a completely different book. If you've got any clues I'd love to hear them. Thanks.

Keeper by Kathi Appelt?

>2 konallis: Found. That was fast. I was just thinking yesterday, based on where I remember shelving it all the time, that it had to be an early alphabet last name, A B or C.