Ian Douglas 
Abyss Deep 

Big, bold military science fiction action from New York Times bestselling author, Ian Douglas.Marines are still the toughest sons of guns in the galaxy.As Bravo Company defuses a hostage crisis on an orbiting mining station, Navy Corpsman Elliot "Doc" Carlyle not only saves the lives of a wounded Marine and two extraterrestrial friendlies – he averts a terrorist strike intended to kill billions. His reward? Deployment on a recon mission into the darkest depths known to man…Abyss Deep is a foreboding ocean planet torn by extremes: boiling storm world on one side, unbroken glacier on the other. Humans established a research colony there to study the planet’s giant sea serpents-but the colony has gone ominously silent. When Carlyle’s team arrives, they discover a vessel belonging to a warlike alien species hovering above the atmosphere. But below the ice lurks a mystery so chilling it will make even Elliot Carlyle’s blood run cold.