An image of debris of the Titan submersible recovered from the ocean floor and the crew’s final message — “all good here” — were among the details shared Monday during the U.S. Coast Guard’s investigatory hearing into what caused the deep-water vessel to implode last year, killing all five on board.

The Titan had suffered more than 100 equipment issues in the two years before the calamity, investigators also revealed, as concerns over safety standards came to light during the first day of testimony.

Tony Nissen, who was hired in 2016 as the engineering director at OceanGate, an underwater exploration company, testified that the relationship between him and its CEO, Stockton Rush, “soured” as the Titan was being completed in early 2018 and set to undergo testing. That year, the submersible was struck by lightning, Nissen said, compromising its experimental carbon fiber hull.

Nissen said there was also a crack in the hull, which he didn’t believe was salvageable, and so he declined to greenlight a planned expedition for the following year.

“I wouldn’t sign off on it,” Nissen testified, “so I got terminated.”

While Nissen was no longer with OceanGate when it made its doomed journey in the North Atlantic Ocean on June, 18, 2023, during a trip to view the Titanic wreck site, his recollections are among the first public comments that will be used to help investigators piece together what led the Titan to implode on its voyage.

Rush, 61, was piloting the Titan, and was killed alongside a French mariner, two businessmen and one of their sons — the youngest passenger at 19 — who brought his Rubik’s Cube on board in hopes of breaking a world record.

Officials said several aspects surrounding the cause of the failure will be examined during the two-week U.S. Coast Guard investigatory hearing in North Charleston, South Carolina. Among the scheduled witnesses before the Marine Board of Investigation are engineers and executives at OceanGate, the Washington state company that developed and operated the Titan, including its co-founder Guillermo Söhnlein.

Jason Neubauer, the chairman of the Marine Board of Investigation, said the hearing’s purpose is to provide necessary safety recommendations for federal and international agencies to consider so that “no family will experience such a loss again.” The board will also determine the extent of any negligence or misconduct, and potential criminality would be referred to the Department of Justice, he said.

Before his firing, Nissen testified that he and Rush had argued over putting the word “experiment” in the waivers that Titan passengers had to sign before they could go on an expedition.

“I made him put it in there,” Nissen said Monday.

He also said Rush had asked him to be the Titan’s pilot on missions to tour the Titanic, but he refused.

“I told him, ‘I’m not getting in it,'” Nissen said, because he didn’t trust the operations crew.

“But I didn’t trust Stockton either,” he added.

Nissen told investigators that OceanGate had no designated safety officer, and Rush got his way at the expense of safety: “Most people would eventually just back down to Stockton.”

On its website before last year’s catastrophe, OceanGate touted that the Titan was made of “titanium and filament wound carbon fiber” and had been “proven to be a safe and comfortable vessel” that could “withstand the enormous pressures of the deep ocean.”

On its website now, OceanGate simply says it “has suspended all exploration and commercial operations.”

Lawyers representing OceanGate were in attendance on the first day of the Coast Guard hearing and permitted to ask questions.

The Titan had lost contact with the Polar Prince, its support ship, almost two hours into its descent to view the Titanic wreckage, which lies at a depth of about 13,000 feet.

OceanGate came under heavy scrutiny as a result of the disaster — an almost unheard-of occurrence in the submersible industry. (Submersibles differ from submarines because they are typically smaller and require support ships or platforms from which to launch and return.)

Experts familiar with the Titan’s design spoke publicly about several potential cost-cutting factors that may have led to the implosion. Those include the 23,000-pound vessel being made with experimental materials such as carbon fiber, which they say has not been pressure-tested over time in such extreme depths, and that the submersible’s hull was fashioned to fit more passengers instead of in a better-known spherical shape.

OceanGate promised voyagers a trip of about two and a half hours to the site, with another four hours of touring the famed sunken ocean liner before returning.

But after the Titan didn’t come back at its scheduled time, the Polar Prince contacted the Coast Guard. Debris from the Titan was found four days later during a search, and while there was a public fascination with how long its passengers could sustain in a cramped tube running out of air, officials said they likely perished instantaneously in a “catastrophic implosion” because the craft could not handle the deep-sea water pressure.

The passengers on board were deep sea explorer Paul-Henri Nargeolet, 77, who was experienced in visiting the Titanic wreck site; British tycoon Hamish Harding, 58; and Pakistani businessman Shahzada Dawood, 48, and his teenage son, Suleman.

The passengers paid $250,000 each for the opportunity to visit the Titanic wreckage, The Associated Press reported.

In the aftermath of the Titan’s implosion, Söhnlein, the OceanGate co-founder who left the company in 2013, insisted that Rush was “very committed to safety.”

“Stockton was one of the most astute risk managers I’d ever met,” Söhnlein said, adding: “When I was there, we always were very transparent with anyone who was going to join us on expeditions about the risks involved.”

But others had raised warnings.

Former employee David Lochridge, who was hired to run manned tests of submersibles, claimed in a 2018 counterclaim lawsuit against OceanGate that he was fired after he warned that the Titan’s carbon shell was not properly tested to ensure it could descend as far as the Titanic.

Lochridge said in the court papers that after complaining that passengers’ lives would be at risk, he was given “10 minutes to immediately clear out his desk.”

OceanGate initially sued Lochridge alleging breach of contract, but the two sides later settled their dispute. Lochridge is expected to provide testimony Tuesday at the Coast Guard’s hearing.

Meanwhile, the estate of Nargeolet filed a $50 million wrongful death lawsuit last month alleging persistent carelessness, recklessness and negligence by OceanGate and others who played a role in its construction. The suit remains ongoing, and Nissen is among those named as a defendant.

Neubauer, the Marine Board of Investigation chairman, said Sunday that the investigation has been one of the most complex for the Coast Guard, due to the nature of the Titan’s incident and the extreme depths at which it occurred, making evidence recovery difficult.

Peter Girguis, a Harvard University professor and adjunct oceanographer in applied ocean engineering and physics at the Woods Hole Oceanographic Institution, said he hopes the hearing will yield an “honest conversation about what led to this tragedy” while making clear that OceanGate’s Titan is not typical of how members of the submersible industry adhere to best practices in design and safety.

The deep ocean should continue to be explored, he added, but said there’s also a larger conversation to be had about whether activities, such as the Titanic tour promoted by OceanGate, on the high seas outside of U.S. jurisdiction, should be regulated.

“We need to support innovators who do think outside of the box, but we have to make sure they don’t bring bodily harm or it results in the loss of life of others who are not complicit in this action,” Girguis said. “The Titan submersible did not just go down with its inventor — it went down with paying passengers.”