Mysteries of the Mist by C.A. Rand
Coralee, who just turned sixteen, is spending her summer vacation at the Silver Wing Point lighthouse with her beloved grandfather. She loves the smell of the briny sea and the way it crashes against the sandy beach and this year she discovers something so fantastical, so secret that she knows this will be the best summer yet.
But a fun vacation soon turns into a stormy disaster when her grandfather goes out to sea and doesn't return. Coralee must rely on the newfound secrets of the sea to save him. Will she do it in time to save his life?
"Perfect for 7+" — Kidliomag review