A group of teens are marooned on a creepy deserted island in Lutz's heart-pounding debut. Diving is in 17-year-old Tasia "Sia" Gianopoulos' blood. Sia's Yiayia (grandmother) spent much of her youth free diving in the waters off Kalymnos, Greece, and now Sia helps her mother lead diving trips in the Florida Keys. She has a bad feeling about diving the wreck of the USS Andrews, but since her father's incarceration for murder they desperately need the money. Sure enough, a client dies, and when a nearby charter, chock full of science students, arrives to help, they're attacked by a giant tentacled creature. Soon after, Sia wakes on an island that shouldn't exist along with her 7-year-old brother, Felix; her crush, Ben, whom she met right before the attack; and his ex-girlfriend, Steph. Simple survival is hard enough without the creature that attacked them lurking right offshore, and a series of disturbing events leads to the island's mysterious heart and a shocking revelation. Lutz strikes the perfect balance of realistic and uncanny, and Sia's dive sequences, in particular, are seriously spooky. While this type of thing has been done before, Lutz does it so darn well that readers won't mind, and the choice to tell the story via Sia's letters to her father adds poignance. Sia's family is Greek American, Ben is cued as black, and Steph is white. An escapist thriller that will reel readers right in. (Science fiction thriller. 13-18) Copyright (c) Kirkus Reviews, used with permission.