Emily Windsnap and the Castle in the Mist by Liz Kessler (author) (UK edition)

The magic ring that Emily finds buried in the sand belongs to King Neptune, and he wants it back. But once on, the ring won’t come off – so furious Neptune puts a terrible curse on Emily. As he sends her boat, Fortuna, spinning through storms and across oceans, Emily is left reeling with questions. Why is Neptune so angry? Why is the ring so special – and what will she find at the strange castle she can see in the middle of the ocean, rising out of the mist…?

“The rich, descriptive passages… conjure a vast watery world governed by violent forces and inhabited by shadowy creatures.” Books for Keeps