Captain Marcus Chaplin
Played by: Andre BraugherThe commander of the USS Colorado — an experienced and well-respected submariner who one day gets a suspicious order to launch nuclear missiles at Pakistan.
- A Father to His Men: was willing to surrender to government authorities in exchange for amnesty for his crew—and in fact was on the verge of signing the deal when it was literally pulled from the table in a double-cross.
- Obfuscating Insanity: How he hopes to prevent anyone from attacking the island. At least, we hope he is faking it.
- Scary Black Man: Played with—if you have exclusive control of an SSBN with 17 Trident missiles on board, and are not acting like you're in your right mind, you're pretty scary no matter what race you are.
- Screw the Rules, I'm Doing What's Right!: Played With, in that Chaplin was following the rules in questioning an illegal order from an unauthorized source, even if it meant going against his chain of command.
Commander Sam Kendal
Played by: Scott SpeedmanThe Colorado's XO. He's willing to follow Chaplin into apparent treason, but the way the government has been treating his wife Christine back home has been shaking his loyalty.
- Married to the Job: According to his wife, she is his "other woman"; he's married to his country.
Lieutenant Grace Shepard
Played by: Daisy BettsThe daughter of Admiral Arthur Shepard, and to all intents and purposes the third in command of the Colorado. She has trouble gaining the respect of the enlisted crew, especially COB Prosser, until commanding the sub on a repair mission, staring down three US attack subs and pulling off a nearly impossible rescue in the process.
- Dude, Where's My Respect?: She's the third-ranking officer and highly capable under pressure, but she's also a young woman, and quite a few people assume she's there because of Nepotism.
- First-Name Basis: In a negative way. Prosser tends to address her by her first name instead of her rank or last name as a sign of disrespect.
- The Neidermeyer: Played With, in that she does eventually gain the respect of the crew and the COB by showing just what she is capable of under pressure.
- Well Done Daughter Gal: Subtle but present; she feels she has a lot to live up to.
Master Chief Joe Prosser
Played by: Robert Patrick.The Chief of Boat (senior enlisted man on the sub), and a close friend of Chaplin until the launch order comes in, at which point he turns on Chaplin and threatens to personally turn him in for treason. Nevertheless, Chaplin can trust him for the time being, because, as Prosser says, if he left, he'd be missing a front row seat for the end of the world.
- Berserk Button: Don't try to peddle drugs to any US Navy personnel or you're in trouble.
- Jerk with a Heart of Gold: Emphasis strongly on "jerk," but he has his moments.
- Father Neptune / Sergeant Rock: Prosser has the loyalty of most of the crew and is clearly the 'old salt' on the boat. Chaplin ultimately has to admit that he can't manage the crew without him.
SEAL Officer James King
Played by: Daniel LissingThe acting commander of the SEAL group picked up in the pilot, and by his own belief the one most directly responsible for the entire fiasco. He has no loyalty to Chaplin or the Colorado, but he's along for the ride, and proves very effective when his services are needed.
- Child Soldiers: King admits to Sam in Manila that he signed up for the military at 17 with fake documents to get away from his family life.
- Dating What Daddy Hates: He was the go-to guy for pissing off girls' dads back in high school.
- Drowning My Sorrows: Almost the first thing he does on the island is find a bar and start a tab.
- I Choose to Stay: In the finale, he decides to remain in the island and begins a relationship with Tani.
Petty Officer First Class Pilar Cortez
- Played By: Jessica Camacho
Played by: Autumn ReeserA young, attractive woman who happens to be the daughter of the owner of a major defense contractor, who's involved in the story because of the Perseus Project, a degaussing device meant to mask a submarine's magnetic field underwater. Though at first glance she seems to be a bit of a promiscuous party girl, she's also very intelligent, manipulative, and determined to both protect her company's project and get to the bottom of the developing scandal in Washington.
- Ambiguously Evil: She's all to happy to use her knowledge of the US Navy blowing up a hundred and fifty Americans on its own submarine to blackmail them into putting her prototype put on more subs, but when it turns out to be something darker, she won't let them sweep it under the rug.
- Blonde Republican Sex Kitten: She's a brunette, but aside from that she is basically the face of the military-industrial complex, and describes herself as "politically straddling a line just to the left of Attila the Hun"
- Jerk with a Heart of Gold: She's pretty bitchy, but also works to help take down the President out of genuine patriotism.
- Rich Bitch: She's aware of it, though, and says she's working on it.
- Spoiled Sweet, although just barely; she's shown to have a rather bratty public persona, but a strong sense of justice behind closed doors.
- Uncertain Doom: Her last scene ends with her moments away from assassinating the President. The odds of her escaping are pretty damn low, but considering at least some members of the Secret Service were in on the plot to over throw him, there's a sliver of hope.
Played by: Jessy SchramKendal's loyal wife, currently fending off governmental gaslighting attempts to break her loyalty, as well as trying to make as much of a scene as possible in front of the press to encourage investigation into the whole mess.
- Cassandra Truth: She knows that her husband (and by extension the Colorado and its crew) is being set up but doesn't help her cause by going ballistic on the media vans parked outside her house—resulting in Christine being painted as a nutjob by the media when footage of her tirade goes viral. The trope may be defied later on now that Christine is talking to the media in a more cooperative fashion (and has gained Kylie Sinclair as an ally on the inside).
- Hair of Gold, Heart of Gold: Despite everything the government throws at her, she never wavers in her belief in Sam.
- Obfuscating Stupidity: It would be easy, especially in the first couple of episodes to think that she's a Dumb Blonde. She isn't.
Played by: Dichen LachmanIntroduced as a bar owner on Sainte Marina in the pilot, Tumrenjak is the daughter of an island native who raised her in Australia, then returned. She became involved with a despondent King when he came into her bar to drink himself blind after Chaplin's mutiny.
- The Bartender: The bar owner, actually, but it's a small bar, so she serves drinks and cleans up.
Played by: Sahr NgaujahThe real power on the island, at least until the Colorado shows up, Serrat is a ruthless drug lord who doesn't deal well with the loss of standing when an American sub captain sails one of the deadliest ships in the world into his harbor.
- Damn, It Feels Good to Be a Gangster: Serrat is undisputedly the top dog on the island until the Colorado shows up (and even Chaplin has to work around him for the time being).
- Joker Immunity: No matter what he does the show comes up with excuse after excuse for Chaplin not to simply kill him.
- Manipulative Bastard: In one episode, he agreed to declare the accused rapist not guilty, knowing the islanders would riot in anger.
- Scary Black Man: at least until he meets up with Chaplin, who's an even scarier black man.
Played by: Camille de PazzisA French civilian NATO employee who helps operate a listening post on Sainte Marina. Her cooperation with the Colorado's crew seems reluctant (especially as she watched the nuking of Pakistan in real time on satellite monitors, nearly having a breakdown in the process), but she's clearly smitten with the very married Kendall.
- All Love Is Unrequited: Her love with Kendall. It leads to her kissing Kendall when he is drugged.