•
Eric Dane as
Commander, later
Captain, and finally
Admiral Tom Chandler, is the former commanding officer of and
chief of naval operations, and instructor at the
United States Naval Academy. •
Rhona Mitra as Dr. Rachel Scott, a paleomicrobiologist who created the vaccine to prevent infection by the virus. (seasons 1-2) •
Adam Baldwin as Commander, later Captain, and finally Admiral Mike Slattery, is the former executive officer and later commanding officer of
Nathan James and chief of naval operations. •
Travis Van Winkle as
Lieutenant Daniel Joshua "Danny" Green is leader of the Naval Mountain Warfare Special Forces Unit aboard
Nathan James. During season 3, Kara worked in St. Louis as
deputy chief of staff to President Michener. In season 4, she returned to duty onboard
Nathan James as the TAO. In season 5, she became the commanding officer of
Nathan James. •
Christina Elmore as
Lieutenant Commander Alisha Granderson is an
officer of the deck on
Nathan James. In season 5, she is serving at
Naval Station Mayport under Admiral Meylan. In season 5, episode 4, she is stabbed to death by her girlfriend, who is revealed to be a spy for Gran Colombia. •
John Pyper-Ferguson as Ken "Tex" Nolan is a private security/military contractor and former
U.S. Army Special Forces soldier who joined the crew at
Guantanamo Bay detention camp. In the season-2 finale, he tracked down his daughter, but learned that his ex-wife was killed by looters. In the third-season finale, Tex was killed stopping Allison Shaw (recurring seasons 1 and 3; starring in season 2; guest in season 5). •
Jocko Sims as Commander Carlton Burk is head of
Nathan James visit, board, search, and seizure (VBSS) teams. In season 5, he is promoted to executive officer of
Nathan James. However, he is killed in the penultimate episode of the show. (recurring season 1; starring seasons 2–5) • Kevin Michael Martin as Chief
Gunner's Mate Eric Miller is a member of the ship's VBSS teams who has worked his way up the enlisted ranks (recurring seasons 1–2, starring season 3–5). •
Bren Foster as
Chief Petty Officer Wolf "Wolf-Man" Taylor is a member of the
Royal Australian Navy CDT 3 (Special Forces) attached to the US Navy Special Warfare Joint Operations Training Program. In season 5, Wolf is a member of Delta Team, a four-man covert-action team (recurring season 2, starring seasons 3–5). •
Bridget Regan as Sasha Cooper, a former Navy Intelligence Officer now operating under diplomatic cover in China for the newly reformed US government, she was once romantically involved with Tom Chandler. In season 5, Sasha is a member of Delta Team (season 3–5). •
LaMonica Garrett as Lieutenant Commander Cameron Burk is the brother of CDR Carlton Burk and the TAO of USS
Nathan James in season 3. In season 4, Burk is wounded in action during an attack on
Naval Station Rota, Spain, which took him off active duty (main in season 3, guest in seasons 4–5). •
Fay Masterson as
Captain Andrea Garnett is the commanding officer of the USS
Jeffrey Michener. Garnett previously served as chief engineer and later executive officer of the
Nathan James. Early in season 5, Captain Garnett is fatally wounded in the surprise aerial attack on Fleet Week by paramilitary forces of Gran Colombia. • Emerson Brooks as Admiral Joseph Meylan is the former commanding officer of USS
Hayward, who joins
Nathan James after his ship was severely damaged by the Chinese Navy. He briefly takes command of
Nathan James ordered by the St. Louis White House (secretly under control of Allison Shaw) to place Captain Chandler under arrest. In season 4, he replaces Andrea Garnett as the executive officer of USS
Nathan James under Captain Mike Slattery. In season 5, he is assigned to Naval Station Mayport as a flag officer (recurring in seasons 3–4, starring in season 5). •
Jodie Turner-Smith as Sergeant Azima Kandie served in the Kenyan Navy for two years; she is part of the VBSS teams on
Nathan James during season 4. In season 5, Azima is a member of Delta Team (recurring in season 4, starring in season 5).
Guests ==Development and production==