The five people aboard the Titan sub have died in a catastrophic implosion of the vessel, the US Coast Guard has confirmed.

A debris field was found overnight at the bottom of the ocean near the Titanic, consistent with a loss of the missing sub’s pressure chamber.

David Mearns, who specialises in deep water search and recovery operations, warned they don’t use phrases like “debris field” unless there’s no chance of a recovery of the men alive.

Speaking to Sky News, Mearns said “a debris field implies a break-up of the submersible … that really sort of indicates the worse case scenario, which is a catastrophic failure, generally that’s an implosion”.

”The only saving grace about that is that it would have been immediate, literally in milliseconds, and the men would have had no idea what was happening.”

From left, Shahzada Dawood, Suleman Dawood, Paul-Henri Nargeolet, Stockton Rush, and Hamish Harding. Image / AP

A US Navy acoustic system, used to detect enemy submarines, detected an “anomaly” on Sunday that was likely the Titan’s fatal implosion, according to a senior military official.

The Navy went back and analysed its acoustic data after the Titan submersible was reported missing on Sunday.

That anomaly was “consistent with an implosion or explosion in the general vicinity of where the Titan submersible was operating when communications were lost,” according to the senior Navy official.

The official spoke on condition of anonymity to discuss a sensitive acoustic detection system.

The Navy passed on the information to the Coast Guard, which continued its search.

The Wall Street Journal first reported the Navy’s involvement.

The five men who perished aboard the sub have all been identified. Among them was a 19-year-old who went on the journey with his dad, who was reportedly obsessed with the Titanic.

Suleman Dawood, the 19-year-old passenger who died aboard the Titan sub, was “terrified” ahead of his trip with his dad to the Titanic wreck, according to his aunt.

Speaking to the NBC, Azmeh Dawood, the older sister of Pakistani billionaire Shahzada Dawood, said 19-year-old Suleman “wasn’t very up for it”.

”I am thinking of Suleman, who is 19, in there, just perhaps gasping for breath ... It’s been crippling, to be honest,” she said.

”I feel like I’ve been caught in a really bad film, with a countdown, but you didn’t know what you’re counting down to… I personally have found it kind of difficult to breathe thinking of them.”

Azmeh Dawood said her brother, who also died in the implosion, was “absolutely obsessed” with the Titanic from an early age.

“He was my baby brother… I held him up when he was born,” she said.Due to the nature of the event, the bodies of the five men may never be recovered.

Earlier: ‘This was a catastrophic implosion of the vessel’

Coast Guard officials told a news conference that they’ve notified the families of the crew of the Titan, which had been missing since Sunday.

The sliver of hope that remained for finding the five men alive was wiped away when the submersible’s 96-hour supply of oxygen was expected to run out and the Coast Guard announced that debris had been found roughly 488m from the Titanic in North Atlantic waters.

“This was a catastrophic implosion of the vessel,” said Rear Admiral John Mauger, of the First Coast Guard District.

US Coast Guard Rear Admiral John Mauger, commander of the First Coast Guard District talks to the media in Boston. Photo / AP

“After the submersible was reported missing Sunday, the US Navy went back and analysed its acoustic data and found an anomaly that was consistent with an implosion or explosion in the general vicinity of where the Titan submersible was operating when communications were lost,” a senior Navy official said.

The official spoke on condition of anonymity to discuss a sensitive acoustic detection system.

The Navy passed on the information to the Coast Guard, which continued its search.

OceanGate Expeditions, the company that owned and operated the submersible, said in a statement that all five people in the vessel, including CEO and pilot Stockton Rush, “have sadly been lost”.

The others on board were: two members of a prominent Pakistani family, Shahzada Dawood and his son Suleman Dawood; British adventurer Hamish Harding; and Titanic expert Paul-Henri Nargeolet.

“These men were true explorers who shared a distinct spirit of adventure, and a deep passion for exploring and protecting the world’s oceans,” OceanGate said in a statement. “We grieve the loss of life and joy they brought to everyone they knew.”

OceanGate has been chronicling the Titanic’s decay and the underwater ecosystem around it via yearly voyages since 2021.

Rescuers rushed ships, planes and other equipment to the site of the disappearance.

Authorities were hoping underwater sounds detected Tuesday and Wednesday might help narrow their search, whose coverage area had been expanded to thousands of miles — twice the size of the state of Connecticut and in water 4km deep.

But the Coast Guard later indicated that the sounds were likely generated by something other than the Titan.

“There doesn’t appear to be any connection between the noises and the location (of the debris) on the seafloor,” Mauger said.

Mauger said it was too soon to say whether the implosion happened at the time of the submersible’s last communication on Sunday. But it was not detected by sonar buoys used by search crews, he said, which suggests it happened before they arrived several days ago.

“We had listening devices in the water throughout and did not hear any signs of catastrophic failure from those,” he said.

The Coast Guard will continue searching near the Titanic for more clues about what happened to the Titan. Efforts to recover the submersible and the remains of the five men who died will also continue, Mauger said.

The White House thanked the US Coast Guard, along with Canadian, British and French partners who helped in the search and rescue efforts.

“Our hearts go out to the families and loved ones of those who lost their lives on the Titan. They have been through a harrowing ordeal over the past few days, and we are keeping them in our thoughts and prayers,” the statement said.

The Titan launched at 6am Sunday and was reported overdue Sunday afternoon about 700km south of St John’s, Newfoundland, as it was on its way to where the Titanic sank more than a century ago. By Thursday, when the oxygen supply was expected to run out, there was little hope of finding the crew alive.

In this photo released by Action Aviation, the submersible Titan is prepared for a dive into a remote area of the Atlantic Ocean on an expedition to the Titanic on June 18, 2023. Photo / AP

Broadcasters around the world started newscasts at the critical hour Thursday with news of the submersible. The Saudi-owned satellite channel Al Arabiya showed a clock on air counting down to their estimate of when the air could potentially run out.

At least 46 people successfully travelled on OceanGate’s submersible to the Titanic wreck site in 2021 and 2022, according to letters the company filed with a US District Court in Norfolk, Virginia, that oversees matters involving the Titanic shipwreck. But questions about the submersible’s safety were raised by former passengers.

One of the company’s first customers likened a dive he made to the site two years ago to a suicide mission.

“Imagine a metal tube a few metres long with a sheet of metal for a floor. You can’t stand. You can’t kneel. Everyone is sitting close to or on top of each other,” said Arthur Loibl, a retired businessman and adventurer from Germany. “You can’t be claustrophobic.”

During the two-and-a-half-hour descent and ascent, the lights were turned off to conserve energy, he said, with the only illumination coming from a fluorescent glow stick.

The dive was repeatedly delayed to fix a problem with the battery and the balancing weights. In total, the voyage took 10-and-a-half hours.

The submersible had seven backup systems to return to the surface, including sandbags and lead pipes that drop off and an inflatable balloon.

Nicolai Roterman, a deep-sea ecologist and lecturer in marine biology at the University of Portsmouth, England, said the disappearance of the Titan highlights the dangers and unknowns of deep-sea tourism.

“Even the most reliable technology can fail, and therefore accidents will happen. With the growth in deep-sea tourism, we must expect more incidents like this.”

- Patrick Whittle and Holly Ramer, NZH