A British billionaire explorer is among the five people on board the missing Titanic tourist submarine, somewhere in the depths of the Atlantic Ocean.

A rescue operation has been underway in search of the submersible vessel, after it submerged Sunday morning, and its support vessel, the Canadian research icebreaker Polar Prince, lost contact with it about an hour and 45 minutes later, authorities said.

Follow live coverage of the missing Titanic sub in our live blog here

British billionaire explorer Hamish Harding, renowned French diver Paul-Henri Nargeolet, founder of OceanGate Expeditions Stockton Rush, Pakistani businessman Shahzada Dawood, and the businessman’s son Sulaiman Dawood are feared to be on board.

Below we look at what we know about the five stranded on the sub.

Hamish Harding

Hamish Harding is chairman of private plane firm Action Aviation, which said he is one of the mission specialists on the five-person OceanGate Expeditions vessel reported overdue on Sunday evening about 435 miles south of St John’s, Newfoundland.

Mr Harding, who has previously travelled on the Challenger Deep to the bottom of the ocean and on Jeff Bezos’ Blue Origin into space, took to Facebook on Saturday to announce that he was joining OceanGate Expeditions for its Titanic mission this week.

On Monday – as news of the missing submersible broke – Mr Harding’s stepson Brian Szasz confirmed that his stepfather was on board the vessel when it went missing.

“Hamish Harding, my step father, has gone missing on submarine. Thoughts and prayers,” he wrote on Facebook, sharing family photos and articles.

The father-of-two is a seasoned explorer and holds three Guinness World Records, including the longest duration at full ocean depth by a crewed vessel when in March 2021, he and ocean explorer Victor Vescovo dived to the lowest depth of the Mariana Trench. In June 2022, he went into space on Blue Origin’s New Shepard rocket.

Paul-Henri Nargeolet

Also on the submarine is French diver Paul-Henri Nargeolet, CBC News was told by Titanic expert Larry Daley. Mr Nargeolet spent 25 years in the French navy and worked with Mr Daley, who is a St John’s-based diver, on his first Titanic dive 20 years ago.

Mr Nargeolet, described by OceanGate as the “Titanic’s greatest explorer”, has since led several expeditions to the Titanic and done 35 dives in the submersible. He is the director of underwater research for RMS Titanic, Inc., which leads expeditions to the wreck that recovers artifacts.

The former naval officer spent his early years in Africa with his parents, although he was born in Chamonix, France. He was married to American newsreader Michelle Marsh until she died in 2017.

Pakistani businessman Shahzada Dawood and his son Sulaiman

Shahzada Dawood and his son Sulaiman Dawood have been named as two of the other people on the submersible in a family statement.

A statement from the Dawood Family, obtained by CNN, said: “As of now, contact has been lost with their submersible craft and there is limited information available.”

“We are very grateful for the concern being shown by our colleagues and friends and would like to request everyone to pray for their safety while granting the family privacy at this time. The family is well looked after and are praying to Allah for the safe return of their family members.”

The pair are understood to live in the UK. Mr Dawood, who is a business advisor and also serves on the board for Prince's Trust International, lives in a Surrey mansion with his wife Christine, son Sulaiman and daughter Alina, according to MailOnline.

The Dawood family is among the richest in Pakistan but has strong links to the UK.

Stockton Rush

OceanGate Expeditions CEO Stockton Rush is also reportedly among those onboard.

His company, which provides crewed submersible services for researchers and explorers to travel deep into the ocean, operates the submersible that has gone missing, the Titan.

After training as a pilot, at the age of 19, Mr Rush became the youngest jet transport-rated pilot in the world.

He also founded the NGO OceanGate Foundation, which helps to make new advances in marine science, history, and archaeology.

Others who have been found safe

Meanwhile, other explorers who were part of the Titanic expedition have confirmed that they are safe.

Deep sea explorer Rory Golden posted on Facebook that he was safe and thanked people for their well-wishes as he said he is now focused on helping “our friends”.

Explorer Renata Rojas also posted about being part of the expedition ahead of Monday’s incident, with a friend commenting that she has spoken to her and she is safe.

OceanGate Expeditions, which offers eight-day tourist missions to see the Titanic wreckage at a cost of $250,000 per person, confirmed on Monday that its submarine was lost at sea with crew members on board.

The company said in a statement to CBS News that it is “exploring and mobilising all options to bring the crew back safely.”

“Our entire focus is on the crewmembers in the submersible and their families,” it said, adding that it is “deeply thankful for the extensive assistance we have received from several government agencies and deep sea companies in our efforts to reestablish contact with the submersible”.

The submersible operates by being launched from a mother ship which then later recovers it at the end of its mission.

A search and rescue operation led by the Boston Coast Guard is currently underway in the Atlantic Ocean.

The company last posted on Twitter on 15 June, detailing its latest Titanic expeditions.

“It’s been an incredibly busy two weeks! Thank you to all of our dive teams who’ve joined us – here’s a look at our Mission 3 and Mission 4 crew,” the company said.

The Titanic, operated by the White Star Line, sank on its maiden voyage across the Atlantic Ocean back in 1912.

The ship – the largest vessel at the time – set sail from Southampton, UK, on 10 April 1912, with more than 2,200 passengers and crew on board headed for New York City.

Five days into its voyage, the Titanic struck an iceberg and sank to the bottom of the ocean. More than 1,500 people died.

In recent years, people have taken trips to visit the wreckage which now lies around 12,500 feet at the bottom of the Atlantic Ocean, approximately 370 miles off the coast of Newfoundland, Canada.

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