San Francisco, Jun 23 (IANS): 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 said 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 -- 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.

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.