The Betrayals of Grim's Peak by Sean J. Quirk
Augie, adopted by Earl and Marge after a hurricane hit the waters, was always afraid of the water. Earl and Marge had even given up using their boat to stay away from the water. But Augie realized it was not fair to Earl and Marge, so they went for a vacation at their old Florida Keys home.
While on vacation, Augie see something he has never seen before and is forced to go into the water in order to learn the truth about what he saw. What he learned was that there is a magical world beneath the surface of the water. While feeling like an outsider, he is befriended by a few select people, and the more he learns, the more he has questions. Even the elders of the underwater world are baffled by what is happening.
Who could ever imagine the world Augie discovers, and who is really telling the truth. Travel with Augie every step of his journey and meet so many characters who don’t always appear to be what they seem.