Plot

In order to make good with his former employers, a submarine captain takes a job with a shadowy backer to search the depths of the Black Sea for a submarine rumored to be loaded with gold.

After a decade of hard work at a marine salvage company, the recently redundant submarine captain, Robinson, decides to risk everything in search of a fabled underwater treasure: a sunken Nazi U-boat laden with gold ingots of inestimable value. Bent on unearthing the unclaimed prize under the nose of the Russians and their hostile naval fleet, Robinson assembles a hand-picked mixed crew of antagonistic experts to comb the vast seabed of the cold Black Sea in a rusty Soviet submarine. However, as greed gets the best of the already divided team, the promise of an equal share rapidly starts to fade away. Can Robinson's men resurface in one piece, and, above all, rich?—Nick Riganas

Follows a captain (Law), who puts together a misfit crew to search for a sunken submarine loaded with gold in the depths of the Black Sea. But greed and desperation soon take hold onboard their claustrophobic vessel and the men start turning on each other, putting them as risk of never making it to the surface alive.

Robinson (Jude Law) is a veteran captain of under-sea salvage who is recently divorced to ex-wife Chrissy (Jodie Whittaker) and estranged from his young son Martin. Robinson receives news that he is to be made redundant (He captained many expeditions for the Agora in his 11 years of employment). He receives 8,640 pounds for his services and is asked to clean his desk and leave the premises. Liam (Karl Davies) is HR for Agora and delivers the news to Robinson that he has been fired. Liam says that under sea salvage has changed and companies are not using submarines any more. Robinson says that he lost his family to the job. Robinson was with the navy for 15 years previously. Due to his unique skills, he cannot land a job anywhere.

Later, while having a drink with some former colleagues, Robinson meets up with his friend Kurston (Daniel Ryan) and a Russian called Blackie (Konstantin Khabensky). Kurston informs the duo of a surefire way to make money. After meeting with Kurston, Robinson agrees to meet with an unknown backer called Lewis (Tobias Menzies) and his executive Daniels.

Daniels tells Robinson that in 1941 Germany was close to total financial collapse, but Stalin was still afraid that Germany will attack Russia. Hitler used this fear to demand a loan of 80 million marks in Gold. Nobody knows what happened as Hitler did invade Russia. But in 1950s a rumor started to circulate that Stalin had complied with the request. Stalin stuffed 2 tons of gold on a submarine sent by Russia. The gold never arrived and that's when Hitler invaded. In the 1980s a Russian ocean research vessel finds a series of ridges on the Georgian coast.

Daniels tells them about a German Type VIIC U-boat from World War II that sank off the coast of the country of Georgia with a cargo of gold worth millions. Robinson says that his former employer Agora found the U-boat's location but was unable to salvage it due to the Russo-Georgian War. He also informs them both of a plan he has been working on to secretly recover the gold. Robinson needs a Submarine and a crew.

Lewis agrees to fund Robinson's expedition on the grounds he receives a 40% split of the proceeds up to $40 million, a 20% cut on any amount above that, and that his executive Daniels (Scoot McNairy) accompany the expedition. Robinson agrees to the deal.

Upon returning home Robinson finds a youth, Tobin (Bobby Schofield), who notifies him of Kurston's suicide (so he can get the insurance money to pay off the Mortgage and buy a comfortable life for his family) and indicates they were friends. Robinson takes the young man in and decides to bring him along on the expedition and acquires a Foxtrot-class submarine from the Port of Sevastopol. It is Blackie who helps arrange the purchase of the submarine. At first inspection Robinson finds 3 escape suits inside the submarine and hides them. The radio was barely working, but Robinson argues that they would not use the radio as they want to hide themselves from the Russian Navy.

The crew is 50% Russian and 50% British and almost immediately there are issues between the two groups. The crew includes Zaytsev (Sergei Puskepalis) (has expertise in submarine engines), Levchenko (Sergei Kolesnikov) (expertise in electric systems and cook), Reynolds (Michael Smiley), Gittens (Branwell Donaghey) (A diver), Fraser (Ben Mendelsohn) (a diver who is a psychopath, and who has been in and out of prison) and Baba (Sergei Veksler) (sonar systems).

Only Blackie speaks Russian and English, and the Russians view the young Tobin as a bad omen, mistakenly assuming he is a virgin when he is in fact an expecting father.

Due to the close confines, tension begins to mount between the two crews. Robinson makes the decision to split the take equally between each crewman. Zaytsev refuses to work with Tobin as he is considered bad luck. The British crew refuses to eat Levchenko's food. Robinson destroys the radio when one of the British crew uses the radio to check lottery numbers. Robinson then burns the lottery ticket. British feel they are sharing too much money with the Russians. Due to the mounting pressures the crew fall out and there is a fight leading to Fraser losing his head and stabbing and killing Blackie. In the ensuing scuffle a fire breaks out and the sub is damaged leading to an explosion which knocks Robinson unconscious.

Robinson wakes up 18 hours later to find tensions at breaking point. The Russians have taken over half of the ship with the British in the other half. The ship is also badly damaged and they have no means to speak with the Russians as Blackie was killed. The sub's drive shaft is damaged, but they discover they are close to the old U-boat and may be able to transfer its drive shaft and save the ship. Tensions continue to mount but Robinson discovers Morozov (Grigoriy Dobrygin) (The navigator) speaks English.

Robinson sends Tobin with Fraser and Gittens to recover the drive-shaft and the gold. While making their way back, third diver Peters (David Threlfall) perishes when his air hose gets cut. Through Morozov they manage to get the Russians to install the drive-shaft and get the sub moving again. At this stage Daniels admits to Robinson that his prior employer set them up such that they are being used to do the dangerous work, while the employer waits to seize the gold as soon as the submarine surfaces. They decide to remain submerged to try to keep the gold and avoid arrest, but while trying to evade the Russian navy they collide with an underwater ridge and come to a stop on the seafloor as the sub begins to take on water.

Fraser and the rest of the remaining crew try to repair the leaks, but their efforts are futile. Before they can escape, a panicked Daniels locks the bulkhead behind him leaving them to drown but traps himself in the next compartment with his snagged clothing. Morozov closes the final bulkhead, protecting Robinson, Tobin, and himself in the torpedo section where Robinson has hidden three escape suits. The torpedo tubes can only be operated from inside the Submarine.

Robinson evacuates Tobin and Morozov and explains to Tobin that he will follow in the third suit using an emergency lever inside the torpedo tube. Both men surface whereupon Morozov informs the young Tobin that there was no emergency lever and that Robinson had chosen to sacrifice himself. Minutes later the third suit appears containing some of the gold and a picture of Robinson's family.