San Francisco: Death likely came very fast to the five passengers on board the Titan submersible and according to submarine experts, the vessel would have imploded and killed its crew so fast that those aboard "never knew it happened".
Ofer Ketter, an expert in submersibles, told The New York Post that the "implosion would occur within a millisecond, if not a nanosecond, if something breached the hull of the vessel to cause a loss in pressure".
They never knew it happened, which is actually very positive in this very negative situation. It was instantaneous
"They never knew it happened, which is actually very positive in this very negative situation. It was instantaneous -- before even their brain could even send a type of message to their body that they're having pain," Ketter, co-founder of a private submersible company called Sub-Merge, was quoted as saying.
More on Titanic sub tragedy
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Debris from the OceanGate Expeditions' Titan submersible was found late on Thursday, confirming all those aboard had died.
By the time communication was lost, the vessel would have been "just shy of 10,000 feet below the surface", experts told The Post.
The five passengers included Hamish Harding, a billionaire and explorer; Paul-Henry Nargeolet, a French explorer; Shahzada Dawood and his son, Suleman Dawood, members of a prominent Pakistani family; and OceanGate CEO Stockton Rush.
The bodies of the five explorers are unlikely to be recovered.
Dr Peter Girguis, oceanographer and Harvard University professor, compared the submersible to a scuba tank.
"When a scuba tank is overfilled, there's a safety device that releases gas very quickly. At least that's the plan. When you take the equivalent of a scuba tank and you want it to hold the pressure out, it's a different story -- because if you go beyond the strength of the vessel, then it crushes or collapses," he said.
Searching for answers to 'catastrophic implosion'
Mystery still surrounds the circumstances that caused the implosion. The bodies of the men have not been recovered and the debris is yet to be fully collected and examined, leaving more to do, maritime experts said.
"We're gonna continue to investigate the site of the debris field ... I know that there's also a lot of questions about how, why and when did this happen?" Rear Adm. John Mauger of the U.S. Coast Guard said at a news conference Thursday.
"Those questions about the regulations that apply and the standards, that's going to be, I'm sure, a focus of future review."
It was important for relatives of the victims to "have an understanding of what happened, [to] begin to find some closure," Mauger said, adding that the site of the debris was an incredibly remote, difficult environment to work in. Given the victims were from different countries around the world, governments would be meeting to discuss "what an investigation of the nature of the casualty might look like."
These men were true explorers who shared a distinct spirit of adventure, and a deep passion for exploring and protecting the world's oceans
Some of the vessels already at the scene, and medical personnel would start to remobilize immediately, he said, while remote operations on the sea floor would continue. Authorities would be "documenting the scene" Mauger said, adding he could not say what the prospects were for recovering the passengers' bodies.
The families of the French navy Cmdr. Paul-Henri Nargeolet; British adventurer Hamish Harding; British Pakistani businessman Shahzada Dawood and his teenage son Suleman Dawood; and OceanGate Expeditions CEO Stockton Rush have expressed their shock and grief.
"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 spokesperson Andrew Von Kerens said in a statement.
According to oceanographer Simon Boxall, a fellow at the University of Southampton's National Oceanography Centre, their bodies are highly unlikely to be recovered, having experienced pressure levels the equivalent of "the Eiffel tower landing on top of you," he said in an interview Friday.
The power of the implosion meant at least that the individuals were probably unaware of what was happening and their death would have been "quick and instantaneous," he added.
Boxall said many people who work in the field had been "fairly certain this was going to happen," but did not want to strike a "defeatist" tone while the widespread search and rescue operation was continuing.
What went wrong?
Now, the focus would shift to piecing together what went wrong, he said, treating it similarly to an air accident investigation. Extensive underwater photography and mapping of the area would likely get underway, followed by using remote-operated vehicles on the ocean floor near the Titanic to gather remaining debris and attempt to reassemble it on land to analyze exactly how and when the implosion occurred.
"It will be a painstaking job," said Boxall, "we're not going to get an answer next week."
Figuring out what happened from a technical perspective could take weeks, agreed John Carlton, director of maritime studies at City, University of London. And any legal battle could take "many months and even years to resolve" because of the loss of life involved, he said in an interview Friday.
"Liability is a complex matter and will have to be discussed by the lawyers as it seems there were several disclaimers that had to be signed by the passengers," Carlton said, noting that jurisdiction would also be a tricky issue with the accident occurring in international waters that don't come under any one nation's legal rules.
The cost of search effort
There are also questions over the final cost of the massive search effort, with some commentators noting that taxpayer-funded government entities were responding to an expedition run by a private corporation.
"It's no different than if a private citizen goes out, and his boat sinks," Paul Zukunft, a retired commandant who led the Coast Guard from 2014 to 2018, said in an interview this week. "We go out and recover him. We don't stick them with the bill after the fact."
The National Association for Search and Rescue recommends against agencies charging for rescue operations, as it may discourage people from seeking help in emergency situations.
The deaths also raise the question of whether the company which operated the vessel, OceanGate, will pay to have the remnants of the vessel recovered - and at what cost.
Zukunft said that typically, the U.S. government pays for the cost of search-and-rescue operations after a crisis at sea, but a private company must decide how and if it will pursue salvage operations once the search is complete.
Recovering debris from the Titan, at a depth of about 13,000 feet, would be a significant and costly endeavor.