Rescuers searching for the missing Titanic sub fear they may never be able to recover the bodies of the five people killed on the expedition.
Rear Admiral John Mauger said: "This is an incredibly unforgiving environment down there on the sea floor and the debris is consistent with a catastrophic implosion of the vessel.
"And so we'll continue to work and continue to search the area down there, but I don't have an answer for prospects at this time."
On Thursday night it was reported that the US Navy detected the likely implosion of the Titan submersible on underwater sound monitoring devices shortly after it disappeared in the Atlantic Ocean on Sunday.
Citing an unnamed senior US Navy official, The Wall Street Journal said the implosion was recorded by a secret acoustic monitoring system designed to detect submarines.
"The US Navy conducted an analysis of acoustic data and detected an anomaly consistent with an implosion or explosion in the general vicinity of where the Titan submersible was operating when communications were lost," the official told the Journal.
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Heavy machinery and rescue submersibles made for a last ditch effort to find Titan as the clock ticked, James Crisp and Nick Allen write.
As time ran out in the search operation on Thursday, reports emerged of a potentially grim discovery from the seabed, close to the Titanic's watery grave.
A "debris field" was found close to the liner's wreckage by one of the ROVs searching the sea bed.
The US Coast Guard quickly confirmed the debris, located near the bow of the Titanic, was the remains of the submersible, and that no one had survived.
James Cameron has said he is "struck by the similarity" of the Titan submersible tragedy and the sinking of the Titanic in 1912.
The Hollywood director said many in the deep submergence engineering community had been "deeply concerned" about the OceanGate Expeditions craft that was reported missing on Sunday.
He told ABC: "A number of the top players in the community even wrote letters to the company, saying that what they were doing was too experimental to carry passengers and they needed to be certified.
"So I'm struck by the similarity of the Titanic disaster itself, where the captain was repeatedly warned about ice ahead of his ship, and yet he steamed at full speed into an ice field on a moonless night and many people died as a result.
"For a very similar tragedy where warnings went unheeded to take place at the same exact site, with all the diving that's going on all around the world - I think it's just astonishing."
Read more: Warnings went unheeded by sub captain, says Titanic director James Cameron
On Thursday the US Coast Guard confirmed the tail cone of the Titan sub was discovered around 1,600ft from the bow of the Titanic wreckage.
The pilot and four passengers of the missing submersible are believed to be dead.
Five major fragments of the 22ft Titan were located in a debris field.
The grim news came after an international search effort in one of the most hostile environments on the planet.
The family of a British billionaire adventurer who died after the Titan submersible suffered a catastrophic implosion have paid tribute to their "dedicated father".
Hamish Harding was described as "a guide, an inspiration, a support, and a living legend" following the news of his death on Thursday.
In a short statement, Mr Harding's family said: "He was one of a kind and we adored him.
"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."
The US Navy detected the likely implosion of the Titan submersible on underwater sound monitoring devices shortly after it disappeared in the Atlantic Ocean during a trip to the wreck of the Titanic, The Wall Street Journal reported.
Citing an unnamed senior US Navy official, the newspaper said the implosion was recorded shortly after the Titan went missing on Sunday by a secret acoustic monitoring system designed to detect submarines.
"The US Navy conducted an analysis of acoustic data and detected an anomaly consistent with an implosion or explosion in the general vicinity of where the Titan submersible was operating when communications were lost," the official told the Journal.