A British businessman and a French explorer were among the five people aboard the Titanic submarine, which went lost 12,500 feet below the ocean.

OceanGate tours, a private organisation that organises deep water tours to explore the debris, verified the disappearance of one of its submersibles, Titan, in a statement.

UK millionaire Hamish Harding is one of the five visitors on board the missing sub, which carries guests 12,500 feet below the surface.

“Thoughts and prayers for my stepfather Hamish Harding as his Submarine has gone missing exploring Titanic,” Mr Harding’s stepson Brian Szasz wrote on Facebook.

“A search and rescue mission is in progress.”

The submarine took out at 4 a.m. on Sunday and had enough air to last until about lunchtime on Thursday.

Its last ping, at 3 p.m. UK time on Monday, one hour and 45 minutes after launch, revealed the Titan was exactly over the wreckage itself, 900 miles off the north-eastern US coast.

Every 15 minutes, pings are meant to be relayed to the mother ship.

OceanGate CEO Stockton Rush, French adventurer Paul Henry Nargeolet, Pakistani billionaire Shahzada Dawood and his son, Suleman are also on board the £195,000 per person expedition.

Meanwhile, Mr. Harding’s buddy, Norwegian adventurer Jannicke Mikkelsen, said she knew he would remain “calm” even throughout the crisis.

“My biggest fear is knowing they’re trapped and can’t get help,” Ms Mikkelsen added.

“There is no one who can reach him at the bottom.”

Titanic expedition leader G. Michael Harris stated he knew several of the individuals on board and that the prognosis was bleak.

He informed Jesse Watters of Fox News that some oxygen was on board, but he was “just not feeling good about it.”

“When we deploy, it’s usually a two-and-a-half-hour drop down to the wreck site itself,” he explained.

“We descend 3,980 metres.” We spiral down at around three degrees per second, landing just in front of the bow of the Titanic.

“Once we get down there, we begin our grid searches, decay, and everything else that goes on with Titanic.”

At a press conference on Monday evening, US Coast Guard Rear Admiral John W Mauger said the force was doing “everything” to find the five people, adding that they were conducting a search 900 miles east of Cape Cod with the Canadian armed forces and commercial vessels in the area.

“It’s a remote area and a challenge, but we’re deploying all available assets to ensure we find the craft and rescue the people onboard,” he added.

According to Mr. Mauger, the submarine’s oxygen supplies would last “somewhere between 70 and the full 96 hours at this point.”

He speculated that the sub may have been entangled in the wreckage and that if so, the Coast Guard would be unable to reach it. An autonomous vehicle capable of reaching depths of 20,000 feet would have to be despatched.

Mr. Harding, a billionaire, announced on social media on Sunday that a ‘window’ had emerged that would allow the plunge to go place.

“We began steaming from St. Johns, Newfoundland, Canada yesterday and plan to begin dive operations around 4 a.m. tomorrow,” he added.

“Until then, we have a lot of preparations and briefings to do.”

Meanwhile, a Titanic veteran diver said he was supposed to be aboard the missing submarine and has been summoned in to help with the search.

David Concannon stated that he had to cancel due to “another urgent client matter.”

“Last night, I was called and asked to provide whatever assistance I could to ensure the safe return of everyone in the sub,” Mr. Concannon posted on the Titanic Book Club Facebook page.

“Of course,” I said, “I immediately agreed.”

The Titanic’s wreck lies more than 12,000 feet below the ocean, approximately 370 miles off the coast of Newfoundland.

Tourists can pay for submersibles to carry them to the ruins, although the cost can exceed £90,000.

OceanGate Expeditions costs up to £195,000 for an eight-day voyage to the wreck, and it recently ran a mission there. On June 16, it last tweeted about a Titanic expedition.

The Titanic, one of the biggest ships in the world at the time of her debut, sank in April 1912, killing over 1,500 of the almost 2,000 persons on board. In 1985, the wreck was located.

James Cameron documented the accident in the 1997 film Titanic, starring Leonardo DiCaprio and Kate Winslet, which grossed over $2 billion at box offices worldwide.

Source: www.lbc.co.uk