The families of those who died after the Titan submersible suffered a catastrophic implosion have paid tribute to their lost loved ones.

It came as it was revealed the US Navy had detected an acoustic signature consistent with an implosion in the general area where the Titan was diving, as long ago as last Sunday – not long after the submersible lost communication with its support ship.

The US Coast Guard has confirmed the tail cone of the deep-sea vessel was discovered near the bow of the Titanic wreckage.

Rear Admiral John Mauger said further debris was also found in the North Atlantic Ocean, off the coast of Newfoundland, that was “consistent with a catastrophic loss of the pressure chamber”.

OceanGate Expeditions said its pilot and chief executive Stockton Rush – along with Mr Harding and fellow UK citizens Shahzada Dawood and his 19-year-old son Suleman Dawood, and French national Paul-Henri Nargeolet – “have sadly been lost”.

British billionaire adventurer Hamish Harding’s family described him as “a guide, an inspiration, a support, and a living legend”, following the news of his death.

Mr Harding’s family paid tribute to the “passionate explorer” in a short statement released on Thursday (US time).

“He was one of a kind and we adored him,” they said.

“He was a passionate explorer – whatever the terrain – who lived his life for his family, his business and for the next adventure.

“What he achieved in his lifetime was truly remarkable and if we can take any small consolation from this tragedy, it’s that we lost him doing what he loved.”

Mr Harding’s family said his death had left a “gap in our lives that can never be filled” and they were “united in grief” with the families of the others who had died.

“We know that Hamish would have been immensely proud to see how nations, experts, industry colleagues and friends came together for the search and we extend our heartfelt thanks for all their efforts,” they said.

Less than a week ago, an excited Mr Harding had posted on social media about joining the expedition to see the wreck of the Titanic.

“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. A weather window has just opened up and we are going to attempt a dive tomorrow,” he wrote on Facebook last Saturday.

“More expedition updates to follow IF the weather holds!”

Sadly, it was his last update.

Shahzada Dawood’s company paid tribute to him and son Suleman after their deaths.

“With heavy hearts and great sadness, we grieve the loss of our vice chairman, Shahzada Dawood, and his beloved son, Suleman Dawood,” Engro Corporation, the Pakistani conglomerate of which Mr Dawood was vice chairman, said in a statement.

“Our thoughts and prayers are with the Dawood family at this tragic time.

“We extend our heartfelt condolences to the family, colleagues, friends and all those around the world who grieve this unthinkable loss.”

From left, Shahzada Dawood, Suleman Dawood, Paul-Henry Nargeolet, Stockton Rush, and Hamish Harding. Photo: AAP

Titan wreckage found on ocean floor

A robotic diving vehicle from a Canadian ship discovered a debris field from the submersible Titan on Thursday morning (local time) on the seabed some 488 metres from the bow of the Titanic.

Rear Admiral Mauger said it was more than four kilometres beneath the surface, in a remote corner of the North Atlantic.

The Titan, operated by the US-based company OceanGate Expeditions, had been missing since it lost contact with its surface support ship on Sunday morning about an hour and 45 minutes into what should have been a two-hour dive to the world’s most famous shipwreck.

Five major fragments of the 6.7-metre Titan were located in the debris field left from its disintegration, including the vessel’s tail cone and two sections of the pressure hull, coast guard officials said.

No mention was made of whether human remains were sighted.

“The debris field here is consistent with a catastrophic implosion of the vehicle,” Rear Admiral Mauger said.

He said it was too early to tell when Titan met its fate but the debris field’s position relatively close to the shipwreck and the time frame of the last communication with the Titan seemed to suggest the failure occurred near the end of its descent on Sunday.

The US Navy acknowledged an analysis of its acoustic data had detected “an anomaly consistent with an implosion or explosion” near the submersible’s location when its communications were lost.

“While not definitive, this information was immediately shared” with commanders of the search mission, a senior navy official said in a statement quoted by the Wall Street Journal.

Citing unnamed US defence officials, the Journal said the sound was picked up by a top-secret system designed to detect enemy submarines.

Filmmaker James Cameron, who directed the Oscar-winning movie Titanic and has been to the wreck in submersibles himself, told Reuters he learned of the acoustic findings within a day and knew what it meant.

“I sent emails to everybody I know and said ‘we’ve lost some friends, the sub had imploded – it’s on the bottom in pieces right now’,” he said.

“I sent that out Monday morning.”

Sonar buoys dropped by aircraft had picked up some sounds on Tuesday and Wednesday that temporarily offered hope the Titan was intact and its occupants were alive and trying to communicate by banging on the hull.

But officials said analysis of the sound was inconclusive and the noises probably emanated from something else.

-with AAP