The owner of the Titan submersible, who died along with four passengers when piloting the craft on its disastrous visit to the wreck of the Titanic, has been described as behaving in a "predatory" manner in the way he tried to seek endorsement for his expeditions.
The Times newspaper reports that Stockton Rush, founder of the OceanGate company, was "struggling to make the operation profitable" and many people in the exploration community had expressed doubts over the safety of his craft.
Patrick Lahey, an experienced undersea vehicle designer, said Rush had even managed to convince informed and knowledgeable people, such as his friend Paul-Henri Nargeolet.
The French explorer was one of the four paying passengers who died in the implosion, along with British aviator Hamish Harding, Pakistani-British businessman Shahzada Dawood, and his 19-year-old son Suleman.
Lahey said he had warned his friend, known as PH, of the risks.
"I told PH that going out there in some way sanctioned this operation. I said: 'You're becoming an ambassador for this thing; people look at you and your record and the life you lead and things you've done, which are extraordinary, and in some ways you are legitimizing what (OceanGate) are doing," he said.
A statement issued by Action Aviation on behalf of Hamish Harding's family paid tribute to a man described as "one of a kind".
"To his team in Action Aviation, he was a guide, an inspiration, a support, and a living legend," it said. "He was a passionate explorer... what he achieved in his lifetime was truly remarkable and if we can take any small consolation from this tragedy, it's that we lost him doing what he loved."
Suleman Dawood's mother, Christine, said he had been fascinated by the Titanic since completing a 10,000-piece Lego model of the ship, which was why she had passed up her place on the craft to let him go instead.
A BBC profile said Rush, who came from a family that had made its fortune through oil and shipping, had an aerospace engineering degree from Princeton University and at 19 became the youngest pilot in the world to qualify for jet transport rating, the highest level of pilot qualification.
He had hoped to be an astronaut and visit Mars, but turned his attention to undersea exploration when that dream faded.
Fellow industry professionals had expressed safety concerns, but Rush dismissed them as "baseless".
In an email from 2018 published after the tragedy, Rob McCallum, a consultant who worked for Ocean-Gate, warned Rush that his attitude was ominously similar to that of the builders of the Titanic, which hit an iceberg on its maiden voyage in April 1912 and sank with the loss of more than 1,500 lives.
"In your race to Titanic you are mirroring that famous catch cry: 'She is unsinkable,'" McCallum wrote to Rush. "As much as I appreciate entrepreneurship and innovation, you are potentially putting an entire industry at risk."
But Rush dismissed his concerns as "baseless cries", heard "way too often", adding "I take this as a serious personal insult".