Fears are growing for the safety of the five people onboard the submarine that went missing during an expedition to the wreckage of the Titanic.
The US Coast Guard has launched a search and rescue operation after they received a phone call to their military branch on Sunday (local time) informing them the Canadian research ship Polar Prince had lost contact with the underwater vessel.
They were overdue on checking with their communications, according to Coast Guard spokesperson Lt. Samantha Corcoran.
"Right now, we are just trying to use all efforts and work with international partners to try to get any resources out there to safely locate all five individuals," she said.
The submarine - with one pilot and four "mission specialists" onboard - began its dive on Sunday morning.
It lost contact an hour and 45 minutes into a dive towards the Titanic wreck, according to the US Coast Guard.
One of those onboard the submersible is UK businessman explorer and billionaire Hamish Harding, his family confirmed.
His stepson took to Facebook to confirm that Harding had "gone missing exploring Titanic" and asked for "thoughts and prayers".
"Thoughts and prayers for my stepfather Hamish Harding as his submersible has gone missing exploring Titanic. Search and rescue mission is underway," the stepson said before subsequently removing the post, citing respect for the family's privacy.
Foreign, Commonwealth and Development Office (FDCO) confirmed they're in contact with the "family of a British man" following reports of a missing submarine off the coast of North America.
Action Aviation, an aviation sales and operations company which Harding is chairman of, confirmed on Twitter the billionaire was part of the Titanic expedition.
Harding's eerie post
But just before Harding went on the submarine, he wrote an eerie post on social media admitting it was the "worst winter in 40 years".
"Due to the worst winter in Newfoundland in 40 years, this mission is likely to be the first and only manned mission to the Titanic in 2023," he wrote.
"A weather window has just opened up and we are going to attempt a dive tomorrow.
"The team on the sub has a couple of legendary explorers, some of which have done over 30 dives to the RMS Titanic since the 1980s including PH Nargeolet."
Other passengers to be identified as being onboard the missing submersible are French submersible pilot Paul-Henry Nargeolet, and chief executive and founder of OceanGate Expeditions Stockton Rush, according to Sky News UK.
The private company that operates the submarine, OceanGate Expeditions, said in a statement on Monday that it was "mobilizing all options" to rescue those on board.
OceanGate managing director Mark Butler told the AP that everyone was "hoping and praying" that the rescue would be a success.
"Every attempt is being made for a rescue mission," Butler said. "There is still plenty of time to facilitate a rescue mission, there is equipment on board for survival in this event."
Between 70 and 96 hours of emergency oxygen left
Rear Adm. John Mauger, the commander of the Coast Guard district in Boston leading the search, told media the occupants would theoretically have between 70 to 96 hours of air as of late Monday afternoon (local time).
"That gives us some time to affect a search," he said. "But when something happens on the high seas, it gets complicated quickly."
It's still unclear whether the submarine was still underwater or had surfaced and was unable to communicate.
Mauger told media the rescue teams "take this personally" and are doing everything possible to bring those onboard "home safe".
"It is a remote area and it is a challenge to conduct a search in that remote area," Mauger said.
"We are deploying all available assets to make sure that we can locate the craft and rescue the people on board. Going into this evening we will continue to fly aircraft and move additional vessels."
The rescue efforts involve sonar, aerial searches and surface vessels and are being carried out in a very remote location.
Part of the operation involves anticipating what capabilities will be needed to rescue those aboard if found.
The expeditions, which cost $250,000 per person, start in St. John's, Newfoundland, before heading out approximately 640km into the Atlantic to the wreckage site, according to OceanGate's website.
The Titanic infamously hit an iceberg on April 14, 1912 during its maiden voyage from Southampton, England to New York City in the US.
More than 1500 of the 2200 passengers onboard drowned that day, in the deadliest sinking of a single ship up to that time.
The Titanic wreck sits about 3800m below sea level at the bottom of the ocean and is located about 600km off the coast of Newfoundland, Canada.
