Titanic submarine: First pics of Titan show it imploded 'in under a second' says expert

One second, they were alive. The next second, the five passengers above the doomed OceanGate submersible were dead — crushed and burned by the immense pressure of the deep sea.

And they probably had at least a bit of warning before it happened, according to an underwater archaeologist.

The wreckage of Titan, the OceanGate submersible that historically imploded during a mission to the site of the Titanic last week, was recently pulled from the sea.

Dr. E. Lee Spence studied the distorted parts of the vessel as crews pulled it ashore and told metro.co.uk that he was initially surprised by the size of the recovered parts.

The passengers aboard Titan likely had warning that it would implode before it did, an expert says (AP)

But then, a new series of events started to make sense, the 76-year-old shipwreck historian and treasure hunter said.

Many would think of the implosion like the crushing of a tin can, Spence said.

His theory, however, postulates that it split open, then flooded, equalising the pressure inside and out.

The implosion itself would have happened instantaneously, in a matter of "microseconds, a fraction of a second," but the passengers would have been alerted to the danger "for at least a few minutes" before it happened.

"The shape of the vessel would start distorting," he said. "There would have been a crack or a leak."

Officials are continuing to investigate the cause of the implosion (Canadian Press/REX/Shutterstock)

"As soon as there was an actual split, the water would have come in at such a pressure that, once it reached the critical point, it would have happened almost instantly," he added.

Spence's theory is a far cry from many of the horrific implosion videos circling TikTok.

One graphic video, posted by user @2pac.thadon, showed a fiery underwater explosion with lots of particulate dispersion and smoke.

Officials from the US, UK, Canada and France are continuing to investigate the incident and are expected to issue a report with recommendations on improving submersible safety.

It's also important to note that, as experienced as Spence is, his theory is just that — a theory. As the investigation continues, more details will become available.

And eventually, we might finally understand exactly what happened on that fateful day last week.