Families of the five people on board the Titan sub have expressed "profound grief" after the US Coast Guard confirmed the crew died following a "catastrophic implosion".
Rear Admiral John Mauger, who led the search for the lost submersible, told a news conference yesterday that debris from the vessel had been found by a remotely operated vehicle about 1,600 feet (487 metres) from the bow of the wreckage of the Titanic in the North Atlantic Ocean.
Speculation is mounting that the US Navy detected an implosion of the submersible soon after it went missing on Sunday.
Exactly what happened to the sub remains unclear, but a senior Navy official reportedly told CNN that an acoustic signature consistent with an implosion was detected soon after it went missing on Sunday.
Here is what we know.
The US Coast Guard said five major pieces of the Titan had been found amid debris around the Titanic site, which was "consistent with catastrophic loss of the pressure chamber".
Submersibles are designed to withstand "crushing underwater pressures" like those at the Titanic wreckage site, explained Insider. The ship sits 12,500 feet down on the Atlantic Ocean floor, where pressure is about 400 times greater than at sea level.
However, any damage or defect to the hull of the vehicle could lead to a leak that would cause the vessel to immediately implode under those extreme pressures.
Commodore David Russell, a former Royal Navy submariner, told Sky News that the evidence suggests that the Titan's pressure hull failed.
An implosion is "basically the exact opposite of an explosion", said Insider. "Instead of pressure from within moving outward," it explained, "you have pressure from outside rushing in."
This tears the vessel into pieces. In common with an explosion, after an implosion "there is unlikely to be much left of the vessel and its cargo".
"I don't think people can appreciate the amazing energy involved in the destructive process of an implosion," oceanographer Bob Ballard told ABC News. "It just takes out and literally shreds everything."
Experts said the five people on board - Paul-Henri Nargeolet, Stockton Rush, Shahzada and Suleman Dawood and Hamish Harding - would not have suffered for long, if at all.
"I know it's no great comfort to the families and the spouses, but they did die instantaneously," journalist David Pogue told CNN. "They were not even aware that anything was wrong."
The implosion would have been almost instantaneous, lasting only milliseconds, said experts. It would have pulled the metal vessel apart "like taffy [chewy sweets]", added Naval History Magazine, quoted on Insider. "Complete destruction" would "occur in 1/20th of a second", too fast to be "cognitively recognized by the men within the submarine".
The chances of recovering the remains of the crew are considered low. "This is an incredibly unforgiving environment," said Mauger when asked if the US Coast Guard would be able to locate the victims' bodies.
But there are hopes of a greater understanding of what went wrong. A potential source of information about what exactly happened might be hydrophones, underwater microphones that are used to listen for illicit atomic weapons tests, explained the BBC.
They have previously helped to establish that the Argentinian submarine San Juan had imploded after it went missing off the country's coast in 2017.
Meanwhile, experts are already questioning the safety of the Titan submersible and demanding that private sector deep-sea expeditions are better regulated.
Court documents cited by the Daily Mail suggest that safety concerns had previously been raised about the Titan submersible by a former employee of OceanGate.
David Lochridge, OceanGate's former director of marine operations, claimed wrongful dismissal after raising concerns about the company's alleged "refusal to conduct critical, non-destructive testing of the experimental design".
Therefore, noted CNN, experts predict "a new push for rules governing new high end, big dollar tourism" of the kind being practised by OceanGate Expeditions.
The Titanic disaster "led to a rethink of international regulations", said the news channel. "Titan may have a similar legacy."