During a trip on board the Titan off the coast of the Bahamas in April 2019, Karl Stanley, an expert in submersibles, knew immediately that something was off: He heard a cracking noise that got only louder over the two hours it took for the submersible to plunge more than 12,000 feet.

The next day, Stanley wrote an email in which he detailed his concerns to Stockton Rush, the chief executive of OceanGate Expeditions, who was also on board the Titan for the dive, urging Rush to cancel the expeditions to the wreck of the Titanic that was planned for that summer.

“A useful thought exercise here would be to imagine the removal of the variables of the investors, the eager mission scientists, your team hungry for success, the press releases already announcing this summer’s dive schedule,” wrote Stanley, according to a copy of the email seen by The New York Times. “Imagine this project was self-funded and on your own schedule. Would you consider taking dozens of other people to the Titanic before you truly knew the source of those sounds??”

The US Coast Guard said on Thursday that a remote-controlled vehicle found debris from the Titan near the wreckage of the Titanic, ending a four-day, multinational search for the 22-foot watercraft that had captivated people worldwide. Rush was piloting the Titan and was among the five people on board who were killed. The Titan’s final voyage would have been its 14th expedition to the Titanic’s wreckage.

Stanley has operated a tourist submersible in Honduras for 25 years, although his vessel descends only to about 610 metres, far less than the more than 3,962 metres that Titan was designed to reach.

Accompanying Stanley on his dive on the Titan in 2019 with Rush was OceanGate’s programme manager, Joel Perry, who Stanley said in his email to Rush shared his concerns about the Titan. Perry, who left OceanGate in 2019, months after the dive, did not immediately respond to a request for comment.

Rush had heavily promoted his plans for the Titan before its first deep-sea dive in 2019. The year before, at a conference of crewed underwater vehicle specialists in New Orleans, several experts confronted Rush directly about their concerns with the Titan in a tense exchange, Stanley said.

Shortly after the conference, more than three dozen industry experts sent Rush a letter urging him to put the Titan through a certification process.

“People were basically ganging up on him in that room,” said Stanley.

Rush was determined to build a submersible with a larger capacity than other such craft, which are metal spheres that can carry three people at most, Stanley said.

In the April 2019 email to Rush, Stanley said the loud cracking sounds that they had heard during their dive “sounded like a flaw/defect in one area being acted on by the tremendous pressures and being crushed/damaged”. He wrote that the loud, cracking noise signalled there was “an area of the hull that is breaking down”.

Rush never replied directly to that email, Stanley said. But he made some changes to the Titan, including building a new hull, and called off the planned dives for that year.

Experts said that one explanation for what might have caused the Titan to implode was that water seeped in where a titanium piece was glued into the end of the vessel’s cylinder.

New York Times News Service

Teen ‘was terrified but went ahead for father’

London: The family of a teenager killed on the Titan sub have said he was “terrified” of the expedition but wanted to go with his dad because it was Father’s Day.

Suleman and his father Shahzada Dawood were among five people who perished on the submersible when it suffered what the US Coast Guard said was a “catastrophic implosion” while diving into the wreck of the Titanic.

US media reported on Thursday that the 19-year-old had expressed hesitation about the trip with his father, the Pakistani-British tycoon.

Azmeh Dawood, his aunt, told NBC News that the teenager had told a relative he “wasn’t very up for it” and felt “terrified”.

The trip was over the Father’s Day weekend and he was keen to please his father, who had a passion for the Titanic, she said. She told NBC News: “I feel disbelief. It’s an unreal situation. I feel like I’ve been caught in a really bad film, with a countdown, but you didn’t know what you’re counting down to.”

The Daily Telegraph, London