From the critically acclaimed author of Float and Glitchcomes a new standalone adventure under the sea, perfect for fans of GordonKorman and Dan Gutman!Berkeley and her best friend, Garth, live on an old cruiseship, scavenging for supplies from the drowned cities left behind on the oceanfloor after the sea swallowed up all the land. They think they've seen every kindof aquatic creature, but they never expected to find sea monsters...After awakening a Hydra, Berkeley and Garth are sent to liveon a submarine, where they study and hunt sea monsters. But the Hydra wantsrevenge on their home ship-and if it succeeds, their families will go down withit.Berkley, Garth, and their crew must find a way to save theship. But monsters aren't the only deadly things lurking in the ocean's depths.