Teams trying to find the submarine that disappeared during a voyage to the Titanic can take heart from a series of successful rescue missions in the past.
These include the Nigerian cook who survived underwater for almost three days by crouching in a bubble, and a castaway who survived 438 days off Mexico.
There was also the astonishing rescue of Roger Mallinson and Roger Chapman, whose mini-submarine plunged 450 meters below the surface in 80 hours of air.
And then there was young fisherman Rolando Omongos who was found at sea off the Philippines in 2017 almost two months after being reported dead.
In one of the largest rescue missions in history in 1939, some 33 men from the US submarine Squalus were rescued after their ship sank 250 feet (74 m) in the ocean.
Here, as rescue efforts continue off the coast of Newfoundland for the stricken tourist submarine Titanic, MailOnline looks at six famous stories on or under the water:
Harrison Okene – Survived in a bubble for nearly three days
Harrison Okene survived nearly three days underwater in May 2013 by crouching in a bubble after his tugboat capsized about 20 miles off the Nigerian coast.
The cook, who was the only survivor in a crew of 12, survived on a single bottle of Coca-Cola to quench his thirst for 62 hours at the bottom of the Atlantic Ocean.
His boat capsized and later rested upside down on the seabed at a depth of about 100 feet, but he was able to survive in the air pocket until rescuers reached him.
Okene said he could smell the dead bodies of his fellow crew members and horribly heard fish eating them as he tried to stay above the surface of the water.
The two flashlights he found gave up after less than a day, but he was eventually rescued by scuba divers who discovered the wreck.
A video captured the astonishing moment he was found when he reached out and touched one of the rescue team members, letting them know he was alive.
Mr Okene suffered nightmares after his ordeal and vowed never to go into the sea again – but he has since become a commercial sky diver to depths of 50 metres.
Harrison Okene survived nearly three days underwater off the Nigerian coast in May 2013
Mr. Okene, second from left, poses in a decompression chamber with members of the DCN Diving team who saved his life after being trapped for three days
Roger Mallinson and Roger Chapman – saved with 12 minutes remaining
Things looked bleak for Roger Mallinson, 35, and Roger Chapman, 28, when their mini-submarine plummeted 1,500 feet below the surface with 80 hours of air.
Working under the Atlantic Ocean 150 miles off the coast of Cork in Ireland, the duo laid a telephone cable in August 1973 in the ship Pisces III.
After being towed to the surface, a faulty hatch to a self-contained compartment broke, water poured in and it sank straight down, breaking the connecting cable along the way.
The craft remained impaled in the seabed, and the submarines had to change carbon dioxide filters every hour to avoid suffocation, using two clockwork timers as alarms.
Three submarines, several ships, planes and helicopters were involved in the rescue, which eventually resulted in them being hoisted up with only 12 minutes of oxygen left.
Mr. Chapman then developed the use of unmanned submarines.
Mr. Mallinson admitted of their ordeal, “Neither of us really thought we’d get out.”
The Pisces III sank 1575 feet below the surface in August 1973 with only 80 hours of air
Roger Mallinson and Roger Chapman celebrate after their rescue from Pisces III in 1973
The front page of the Daily Mail tells the story of the rescue effort to get the men to safety
Rolando Omongos – Rescued after being adrift on a small boat for two months
A young fisherman from the Philippines was given up for dead at sea, where he battled hunger, thirst and despair on a small boat for nearly two months.
Rolando Omongos, who was 21 years old when his ship drifted all the way to Papua New Guinea, was finally rescued by a Japanese ship in 2017.
He said he survived on rainwater and moss growing on the hull of his eight-foot boat, and that he found respite from the heat of the sun by regularly diving into the water.
His 31-year-old uncle Reniel Omongos, who was on a second small boat, died after a month. Rolando believed that starvation and exposure killed him.
The family members had departed in December 2016 with other fishermen aboard a purse seiner from General Santos, a southern Philippine port overlooking the Celebes Sea.
A storm separated Rolando and his uncle from their mother boat in January 2017, and they ran out of fuel five days later. But he said, “I never lost hope.”
Rolando Omongos from the Philippines was rescued in 2017 by a Japanese fishing vessel
Jose Salvador Alvarenga – Castaway survived 438 days at sea
Castaway Jose Salvador Alvarenga survived 438 days adrift at sea, claiming he survived by drinking urine and turtle blood and eating fish and birds he caught.
The tuna fisherman from El Salvador washed up in the Marshall Islands in January 2014 after drifting 6,700 miles off the coast of Mexico since November 2012.
The boat he and crew member Ezequiel Cordoba were sailing in was crippled by a storm, but Mr. Alvarenga later related how his best friend starved to death.
Mr Cordoba’s family sensationally claimed that he was a victim of cannibalism, but Mr Alvarenga denied this, saying he had thrown the body into the water.
He was in surprisingly good health after his ordeal, having claimed to have become so hungry that he grabbed jellyfish from the water and swallowed them whole.
Mr Alvarenga later said he almost gave up hope of rescue after several large vessels came close to his small fishing boat, but no one tried to rescue him.
Jose Salvador Alvarenga steps off a boat after being found in the Marshall Islands in 2014
Jose Salvador Alvarenga attends a press conference in February 2014 after his rescue
Brett Archibald – Floated for 29 hours without a life jacket
Brett Archibald fell overboard from a tour boat in Indonesia in 2013 and drifted 11 miles, but survived by floating for 29 hours – despite not wearing a life jacket.
The South African father-of-two said he nearly drowned at least eight times during the ordeal, being stung by jellyfish and attacked by seagulls.
Mr Archibald was finally picked from the Mentawai Strait by Australian surfer Dave Carbon with a dangerously low blood pressure of 68/44.
His face and head were badly burned, his tongue was swollen, his eyes were red and sore, and his nose had a huge hole where the seagulls had pecked it.
A few months after his ordeal, he endured two severe panic attacks, but began speaking publicly about his experiences and raising money for charitable causes.
Mr Archibald also wrote about his horrific story in a book called Alone: Lost Overboard In The Indian Ocean which was serialized in the Daily Mail in 2016.
Brett Archibald is brought to safety after being rescued from the Mentawai Strait off the coast of Indonesia
Brett Archibald is greeted by his wife Anita and children Jamie and Zara after his rescue
Squalus rescue – 33 men rescued after submarine sank in 1939
One of the most famous submarine rescue missions dates back nearly a century, when the US ship Squalus sank 250 feet off the US East Coast in 1939.
The ship was off the coast of New Hampshire with 56 Navy personnel and three civilians on board when the engine room flooded due to an air valve malfunction.
About 26 men drowned, but the other 33 in the forward compartments sent a location marker and used Morse code to communicate with Navy rescuers.
While they waited, those trapped on board also faced the risk of chlorine gas leaking from the battery compartment.
But all 33 men were removed from the craft with a newly developed rescue chamber, with a few emerging at a time in a 13-hour process.
Survivors of the Squalus disaster are rescued from the diving bell in 1939
The US submarine Squalus sank 240 feet off the US East Coast in 1939
A photograph of the salvage vessel Falcon during the Squalus crew rescue mission