The families and friends of the five people on board the submarine-like vessel trapped beneath the Atlantic Ocean made a desperate plea for people to pray for their safe return.
Pakistani British-based businessman Shahzada Dawood and his 19-year-old son, Sulaiman Dawood, were confirmed to be on the submersible.
Their identities followed British billionaire adventurer Hamish Harding who is also in the vessel, along with French submersible pilot Paul-Henry Nargeolet, and chief executive and founder of OceanGate Expeditions, Stockton Rush.
The five people all paid close to £200k for a ticket on the 21ft vessel for what should have been an eight-hour trip to the bottom of the Atlantic to see the Titanic shipwreck.
But it lost contact around an hour and 45 minutes after it submerged and rescuers warn they may not reach the ocean craft before its oxygen supply runs out.
As people from across the globe have spoken out in horror about what has happened, the Dawood and Harding families say they are grateful for all the kind messages of concern and support but wish for privacy.
Their families now have an agonising wait to see if naval teams from across the US, Canada and the UK can rescue their beloved before the oxygen onboard runs out in around 50 hours.
One explorer and friend of missing British billionaire Hamish told Sky News she is "terrified" that the five could be at the bottom of the ocean running out of air.
"This is what I fear the most," Jannicke Mikkelsen said.
The father and son, who are both British citizens, belong to one of Pakistan's most prominent families.
The Dawood mother and daughter say they are "praying to Allah" for the safe return of their beloved father and son.
Private plane firm Action Aviation said the family of its missing chairman Hamish Harding are "very grateful" for the "kind messages” and they have chosen to express optimism over a rescue, saying they "look forward to welcoming him home."
The first British diver to see the wreck of the Titanic said that Paul-Henry is an “extraordinary explorer and an incredible individual”.
Dik Barton, who made 22 dives to the wreck, said the group had “good leadership” in pilot Paul-Henry as "he knows the wreck better than anybody."
Dik continued: "He is the kind of man who will keep them calm, but it’s not easy in a tube at the bottom of the ocean."
David Mearns also knows Paul Henry professionally and is personal friends with Hamish.
Mr Mearns said: "When I found out initially that Hamish was on board that was very upsetting and then when later in the day that PH was also with him on the sub, which was almost a typical thing to expect, they would have got on fantastically well these two characters, that really started to make the day a lot worse."
Oceanologist Dr Simon Boxall, of the University of Southampton, said a distress signal was sent out by the submarine.
Dr Boxall said: "This is second-hand knowledge but my understanding is that they have received a signal from the submarine.
"You can't use radios underwater. You rely totally on 'pings'. What they have is really limited communication.
"Apparently they have had, and I don't know when ... they have had an emergency ping saying the vessel is in distress.
“I don't know if that is automatically generated or generated by people on board.
"It could be that the vessel is lost already or it could be automatic."
The Foreign Office says it is aiding the families of three British nationals on the missing Titan submersible.
The Titanic's wreck lies 435 miles south of St John's Newfoundland, with the recuse mission being run from Boston, Massachusetts.
At a press conference about the missing submarine, Rear Adm. John Mauger confirmed that was designed with 96 hour emergency oxygen capability
"We anticipate there is somewhere between 70 and the full 96 hours available at this point," Mauger says.
Speaking from where the rescue operation was being led in Boston, Rear Admiral John Mauger, said “everything was being done” to find the submersible.
He said it included specialised submarine detection planes, the US Coastguard, the Canadian military, and commercial ships.
Sonar buoys that can listen to a depth of 13,000ft have been placed in the water.
The Titanic lies at 12,500ft on the ocean bed.
In a short statement released today, a spokesperson said: "We are in contact with the families of three British nationals following a submersible going missing off the coast of North America and are in touch with the local authorities."
