Debris Confirms Titan Submersible Loss; Experts Weigh Likely Scenarios Behind the Fatal Failure

On Thursday, OceanGate Expeditions said the five people aboard its Titan submersible are believed to be dead. The announcement came after rescue officials found debris they linked to the vessel, ending a search that had gone on for days off the coast of Cape Cod, Massachusetts.

The Titan weighed 23,000 pounds and was owned by OceanGate. According to the US Coast Guard, it dropped off the radar about one hour and 45 minutes into its descent toward the Titanic wreck. Aboard were OceanGate's CEO, a British billionaire adventurer, a French diver and explorer, and a father and son from Pakistan.

The debris was found roughly 1,600 feet from the Titanic site. That location ruled out the most hopeful possibility experts had discussed, that the sub had resurfaced and was simply waiting to be found. Stefan Williams, a professor of marine robotics at the University of Sydney, had called that the best-case scenario. On Tuesday he said it looked increasingly unlikely as time passed. Retired Navy Rear Adm. Chris Parry told Sky News the same day that a sub on the surface would have been found by now.

The scenario experts considered most likely was a catastrophic failure. Williams said it could have started with a leak, a power failure, or a small electrical fire that knocked out the systems used for navigation and control. The worst case was a breach of the pressure hull, leading to an implosion. In his words, that would happen quickly, with little chance of survival. In 2018, a submarine pilot hired to assess the vessel had warned that its hull monitoring system would detect failure only, in his words, often milliseconds before an implosion. The Coast Guard said Thursday it is still investigating what happened before the implosion.

The third scenario was that the Titan was intact but stuck on the bottom. The Titanic lies at about 12,500 feet, and the Titan was rated to carry five people to 13,123 feet. Frank Owen, a retired Royal Australian Navy official and project director for submarine escape and rescue, told The Guardian the wreck is surrounded by debris from the disaster more than a century ago, and that parts of it are all over the place and dangerous. Williams called entanglement unlikely but not impossible.

Hope had flared earlier in the week over underwater noises. The Coast Guard confirmed Wednesday that sonobuoys, sensitive microphones on buoys dropped from planes, had picked up suspicious sounds. Rolling Stone reported that searchers on a Canadian aircraft detected banging at 30-minute intervals. Owen told the BBC his confidence went up by an order of magnitude. Williams was more cautious: even if the crew were alive, he said, they faced the hard task of getting the sub to the surface, and their air was running out. On Thursday the Coast Guard said there did not appear to be any connection between the noises and the location on the sea floor.

A rescue would also have been an unprecedented problem. Alistair Greig, a professor of marine engineering at University College London, told The Guardian that very few vessels can reach such depths, and certainly not divers. Experts had estimated the oxygen would run out around Thursday morning, though Matthew Schanck of MarSAR International noted that PH Nargeolet, a seasoned diver aboard, might have known how to stretch the supply. Capt. Jamie Frederick of the First Coast Guard District had said Wednesday that officials had to remain optimistic and hopeful.

What remains is the investigation. Coast Guard officials are examining the debris and its location for answers about what happened before the implosion.