The deep-sea search for OceanGate’s Titan sub has ended, the U.S. Coast Guard announced it suffered a “catastrophic implosion” on Sunday. Watch the Titan Implosion simulation here.

The Titan submersible was on its way to see the remains of the Titanic on Sunday when it imploded in milliseconds. Its five passengers, Hamish Harding, Shahzada Dawood, Suleman Dawood, OceanGate CEO Stockton Rush and Paul-Henri Nargeolet, were all killed in the tragedy.

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As per CNN, U.S. Coast Guard Rear Admiral John Mauger, the First Coast Guard District commander, said in a press conference: “The debris is consistent with a catastrophic implosion of the vessel.”

According to the Wall Street Journal, search officials said the U.S. Navy first heard sounds of the implosion hours after the Titan passengers embarked. How? With a “top-secret” acoustic detection system used to spot enemy submarines.

The Navy communicated its findings to the search, but the implosion hypothesis was “not definitive” until days later.

After confirming the implosion happened in milliseconds, many people wonder how that would have looked or felt for the victims. A TikTok video simulation shows how it happened, leading one user to comment: “At least [passengers would] have known absolutely nothing about it.”

The Titan sub suffered a “catastrophic implosion” on Sunday, as per U.S. authorities

The submersible’s “implosion” was confirmed Thursday morning after a remotely-operated vehicle found debris from the Titan.

Paul Hankins, director of salvage operations and ocean engineering at the U.S. Navy, explained at a press conference, “The initial thing we found was the nose cone.”

“We then found a large debris field,” he recalled. “Within that large debris field, we found the front end bell of the pressure hull. That was the first indication that there was a catastrophic event.”

Authorities found the debris 1,600 feet from the Titanic’s bow, about 13,000 feet deep in the ocean. Here is a depiction of just how deep the sub would have had to travel to see the historic ship’s remains:

One thing on many people’s minds — did the five passengers feel the implosion as it happened? According to experts, not likely.

As a submarine expert and university professor, Eric Fusil, explained to Australian Broadcasting Corporation, “[Titan passengers] wouldn’t have realized they were dying because they cannot process that information that quickly.”

In fact, Fusil told USA Today that it would take just “20 milliseconds to crush a hull” at that pressure. “So it’s nearly instantaneous and it’s absolutely very, very noisy.”

And why did the implosion happen in the first place? As per ABC, it likely imploded after the pressure vessel failed. U.S. Coast Guard Rear Admiral Mauger agreed the debris was consistent with an implosion caused by the loss of the sub’s pressure chamber.

The simulation gives more insight into what happened

A TikTok video with Titan Implosion simulation by @starfieldstudio theorizes what the “catastrophic” implosion may have looked like, even if passengers did not realize it occurred.

You can see the OceanGate Titan sub descend before experiencing an “instant collapse of the pressure.”

The video of the Titan Implosion simulation explains, “The hull would immediately heat the air in the sub to around the surface of the sun’s temperature.”

“A wall of metal and seawater smashed one end of the boat to the other,” it says, “all in around 30 milliseconds.”

While not an official hypothesis, it shows what a sub-implosion looks like and how quick it is — which, as one TikTok user said, “Is the best-case scenario at this point.”

Other users agree, saying, “This is the best scenario, the worst would be slowly suffocating to death.”

Over on Twitter, another user sped up the video to “the actual speed of the implosion,” considering it probably happened in milliseconds:

Another reference many people watch to get an accurate picture of the Titan sub implosion? This unearthed YouTube video, which shows the implosion of a railroad tank:

Still, as one commenter noted, “This is vacuum pressure, which is 14.7 psi. At the depth the sub would have imploded, the pressure is around 5,800 psi.”