June 23, 2023 - Missing Titanic sub crew killed after 'catastrophic implosion'

The design of the Titan submersible “demanded special extra attention,” according to William Kohnen, chair of the Marine Technology Society’s manned underwater vehicles committee, adding that he had conversations with the late OceanGate CEO to express his concerns about the company's approach to submersibles.

Kohnen, who is also president of the Hydrospace Group, said he made requests to OceanGate to make its website more transparent to spell out that the Titan design was “experimental” and “not certified.” They ultimately changed it, he said.

Speaking to Anderson Cooper on "CNN This Morning," Kohnen said the carbon fiber hull “demanded special extra attention just because that had never been done before.” It meant an “additional effort and probably quite a bit of extra testing to get passed through that certification process,” he said.

The small community of submersible experts had numerous conversations with the late OceanGate CEO Stockton Rush, Kohnen said, and they issued a letter essentially saying, "you are going really, really fast over here and you’re ignoring some of the knowledge base that we have for these things." 

Kohnen said Rush's response amounted to “the existing regulations are stifling innovation and it’s too slow, and we have a better method.”

He called for full disclosure in the industry. “Just tell the public this is not certified, this is experimental, and then it leaves some of the decisions to people to make," he added.

CNN's Nic Anderson contributed to this post.

Dr. Michael Guillen, a scientist, journalist and author who was the first TV correspondent to report from the Titanic, said he thinks ocean tourism needs to be paused following the deaths of the five people aboard the Titan submersible.

Guillen survived a close call in 2000, when he says the submersible he was in got caught in an underwater current, causing a collision with the propeller of the Titanic wreck.

He said there are two main reasons for taking a pause, based on his experience.

"Second of all, what I took away from my trip down there was that this isn't just a shipwreck. I went down there thinking I'm just going to report on a shipwreck, but what hit me — especially in that moment of prayer, and it came home to me — that people lost their lives. Men, women and children. More than 1,000 of them. This is their final resting place. This is sacred ground," he said.

"I think we should pause, figure out what happened so we can fix it in the future, but also think of the danger and think of the sacredness of this site. It's not a joyride. It's not a Disneyland destination," he added.

The Titan submersible that went missing Sunday during a trip to view the wreckage of the Titanic suffered a "catastrophic implosion" and killed five people on board, officials said Thursday.

The submersible had originally embarked on a journey into the depths of the sea off Canada's coast.

Titan's ultimate destination was the Titanic's wreckage, which sits at the bottom of the ocean nearly 13,000 feet below the surface southeast of Newfoundland.

As authorities now seek to better understand what went wrong with the sub, they're dealing with an "incredibly complex operating environment on the sea floor, over two miles beneath the surface," a US Coast Guard official said Thursday.

Here's a look at a map of the area:

Explorer Paul-Henri Nargeolet, who was aboard the Titanic-bound submarine that imploded, will be remembered for his passion for his family and underwater exploration, his stepson John Paschall told CNN.

Paschall said Nargeolet was "someone that you instantly connected with and loved, and shared so many great stories with," and his fascination with the underwater expedition of the Titanic intrigued him to share the stories of the past with people. 

Paschall said Nargeolet was a "big loveable guy who [was] a prankster, but he cared so much about his family and everything he did in life."

Paschall said he was fortunate to have Nargeolet as a stepfather and even celebrated special moments together: Nargeolet and his mother, who died of cancer, once drove 16 hours overnight from Chicago to New York to watch him graduate.

He last saw Nargeolet in May and planned to meet with his stepfather in early July to connect. He said he didn't think twice when Nargeolet set out on one of many expeditions, where he would later lose his life.

The search for more debris from the Titan submersible continues Friday as officials try to piece together a timeline of the vessel's final moments.

On Thursday, authorities said the five passengers on the sub that was diving 13,000 feet to view the wreckage of the Titanic on the ocean floor died in a "catastrophic implosion," bookending an extraordinary five-day international search operation.

Here's what we know:

The Polar Prince, a vessel used to transport the Titan submersible to the site of the Titanic wreckage, is departing the area today.

It will return to St. John's, Canada, either late Friday or early Saturday morning, a source with Horizon Maritime, the company that owns the ship, told CNN.

Marine traffic-tracking sites show a line of several other ships also headed back to St. John's this morning.

UK Prime Minister Rishi Sunak's thoughts are "very much" with the loved ones of those that perished on the Titan submersible, his spokesperson said Friday, according to the UK Press Association. 

UK Foreign Secretary James Cleverly on Thursday expressed his condolences and said the UK government is closely supporting the families of the British citizens who died on board the Titan submersible. 

Three British citizens were onboard: Hamish Harding, Shahzada Dawood and his son, Suleman.

OceanGate co-founder Guillermo Sohnlein cautioned rushing to judgment without the data following the catastrophic loss of the submersible.

Sohnlein left the company in 2013 and was not involved with the voyage or the development of the Titan submersible. He still maintains minority ownership of OceanGate.

He added, “safety was the number one priority” for himself and CEO Stockton Rush who perished along with four others on board.

“He was a very strong risk manager, and I believe that he believed that every innovation that he created — whether technologically or within the dive operations — was to both expand the capability of humanity exploring the oceans while also improving the safety of those doing it,” he said.

A friend of Paul Henri Nargeolet, who was aboard the Titan submersible that imploded over the weekend, described the explorer as an “incredibly talented iconic legendary – the greatest deep diver that the world has ever known."

Speaking to Anderson Cooper on CNN This Morning on Friday, Alfred Hagen recalled a previous trip on which he descended with Nargeolet in the Titan sub to the Titanic wreckage.

When descending, Hagen said the vessel is essentially in a “free fall” and when it reached the bottom, crewmembers had to “find the Titanic,” the bow and stern of which he describes are a “considerable distance apart."

It was a “world of perpetual midnight, and then suddenly if you’re lucky you see the ship appear out of the darkness,” he added.

“I don’t regret going, I do regret that I won’t be able to go again with PH."

When they reached the bottom, he said, “PH would take over flying."

“As far as the safety concerns, of course you were concerned, we all understood the risk we were taking.”

“There was a moment when the current kind of pushed us in closer than we intended and we got stuck and PH was able to maneuver us out and of course at that moment the thought flashes through your mind of – if we don’t get loose this could be it, but I was – that’s a risk that you accept,” Hagen said.

“And I’m tired of people coming in now to insult the high achievers and disparage wealthy people that want to break trail for the rest of humanity.

“These are risk takers, risk takers have always driven humanity forward and taking risk is what distinguishes us as men, and it’s the divine spark."

As for Nargeolet, Hagen fondly recalled him being “equally at ease on the deck of a ship in a hurricane or sitting conversing in a Parisian café.”

Hagen said the loss of his friend had “broken my heart that a man of his dynamism will no longer shine his light in this world.”