Emily Windsnap (abridged)

Emily lives on a boat, but her mother has always been oddly anxious to keep her out of the water, and it is only when she has her first school swimming lesson that she discovers it is her natural element. As soon as she gets into the sea, she grows a tail!

Emily Windsnap is thrilled to arrive at her new home, a secret island near the Bermuda Triangle where humans and merfolk live together, and where being a girl who grows a tail as soon as she enters the water isn't a problem. Being Emily, she can't resist exploring forbidden places, and as a result, she inadvertently wakes the kraken, the legendary deep sea monster who has been asleep for two hundred years.

The magic ring that Emily Windsnap - half mermaid, half ordinary girl - finds buried in the sand belongs to Neptune, and he wants it back. But the ring, once on, won't come off, and Neptune puts a terrible curse on Emily.