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.
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.
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.
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.
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.
Petty Officer First Class Pilar Cortez
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.
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.
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.
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.
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.