Soldes Oshenerth by Foster, Alan Dean NEUF

An epic fantasy that takes place entirely underwater.

In this adventure under the sea, Oshenerth: Blue Magic, New York Times bestselling author Alan Dean Foster (Alien, Star Wars: Force Awakens) uses his extensive knowledge and experience from diving and traveling to bring to life the mysterious world of reef dwellers under the sea in an imaginative, fascinating new epic fantasy that takes place entirely underwater.

Best friends Chachel and Glint, a merson and a cuttlefish, are returning from a shark hunt when they stumble upon an unconscious female demon. Taking her back to their reef community to recover, while they decide what to do with her, they wind up stumbling into a unique friendship, one which will change their lives and community for better as the reef dwellers and the demon together fight to preserve themselves and their way of life in the face of enemies and their blue magic.