When the Titan submersible went missing during a dive to the wreck of the Titanic in 2023, David Lochridge hoped the five people on board – including his former boss – could be rescued.

“I always hoped that what happened wouldn’t happen. But I just knew if they kept carrying on the way they were going and with that deficient equipment, then there would be an incident,” he told the BBC.

The whistleblower had been sacked by the firm behind the sub, Oceangate, after warning about safety issues in 2018.

In June 2023 the sub imploded killing all five people on board – including Oceangate CEO Stockton Rush.

A report from the US Coast Guard (USCG) published on Tuesday found that Oceangate’s failures over safety, testing and maintenance were the main cause of the disaster.

“There is so much that could have been done differently. From the initial design, to the build, to the operations – people were sold a lie,” Lochridge told the BBC.

But he firmly believes the US authorities could – and should – have done more to stop Oceangate.

Lochridge had joined Oceangate seven years earlier as the company’s Director of Marine Operations. He moved his family from Scotland to the US, and was full of excitement about the company’s ambitions.

Oceangate was building a new submersible to take paying passengers down to the most famous wreck in the world – the Titanic.

And he was going to be involved in the project from the very start, working alongside the team designing the sub.

The straight-talking Glaswegian has worked at sea for more than 25 years, first with the Royal Navy and later as a submersible pilot. He also led submarine rescue operations, responding to distress calls from people trapped underwater. He knows about the risks involved in deep dives.

His responsibilities included planning dives and, as chief pilot, he would be the one taking the sub and its passengers 3,800m beneath the waves to see the Titanic. Safety was at the heart of his role.

“As the director of marine operations, I’m the one responsible for everybody,” he told BBC News. “I was responsible for the safety of all Oceangate personnel and all of the passengers that were going to be coming in the sub.”

A prototype for the new submersible, which would eventually be called Titan, was being developed with the University of Washington Applied Physics Laboratory (APL). The plan was to build its hull – the part where the passengers would sit – out of carbon fibre.

No deep diving sub had been made out of this material before – most have hulls constructed from titanium or steel. But Lochridge had confidence in the APL team.

He said he was told by Oceangate’s CEO Stockton Rush that the craft would undergo a safety assessment by an independent marine organisation, known as certification.

Lochridge was adamant that this third-party oversight was essential – especially because Titan was to be made of experimental materials.

But by the summer of 2016 he was starting to have doubts about the project.

Oceangate stopped working with APL and decided to bring the design and construction of Titan in-house.

Lochridge was worried. He didn’t have the same confidence in Oceangate’s engineers. He told the BBC he didn’t think they had experience of building subs able to withstand the immense pressures found at the depth of the Titanic.

“At that point, I started asking questions… and I felt I had a duty of care to keep asking them,” he said.

As the parts for Titan began to arrive, and the craft started to take shape, Lochridge said he was spotting problem after problem.

“When the carbon hull came in, it was an absolute mess,” he said.

He saw visible gaps in the material, areas where the layers of carbon fibre were coming apart – known as delamination.

And he identified issues with other key components.

The carbon fibre hull had titanium domes fitted on each end, but he said the metal had been machined incorrectly. He was also worried that the sub’s view port had not been designed to work at extreme depths.

Most concerning, he learnt that Titan was not going to be independently certified for safety.

He told the BBC that he had always been outspoken on safety issues – so he wasn’t going to stay silent.

“I brought up all the issues that I was seeing… but I was just met with resistance all the way,” he said.

In January 2018, he outlined his concerns again to Stockton Rush. This time Rush asked him to complete an inspection of the vessel.

Titan was at a crucial point of its development. Passengers had already paid deposits for dives to the Titanic planned for later that year. Test dives were about to start in the Bahamas before those expeditions got underway.

Lochridge wanted Oceangate to delay these plans.

“I formulated a report and I sent it out to all the directors in the company.”

The following day he was summoned to a meeting with Rush and several other Oceangate employees.

A transcript from the two-hour-long meeting, where the itemised report was picked over, reveals a heated exchange between Lochridge and Rush.

Towards the end of the meeting, in response to Lochridge’s safety concerns, Rush says: “I have no desire to die. I’ve got a nice granddaughter. I’m going to be around. I understand this kind of risk, and I’m going into it with eyes open, and I think this is one of the safest things I will ever do.”

To Lochridge’s surprise, immediately after this meeting he was fired.

But he was so concerned about Titan that he got in touch with the US government’s Occupational Safety and Health Administration – OSHA.

OSHA told him his case was urgent because it involved public safety and that he would be placed under the whistleblower protection scheme, designed to protect employees from retaliation by employers if they’ve reported concerns about workplace safety.

As part of this process, OSHA passed Lochridge’s concerns about Titan to the US Coast Guard (USCG) in February 2018.

But Lochridge says after OSHA wrote to Oceangate to tell them it was starting an investigation, everything changed.

In March, Oceangate asked Lochridge to drop the OSHA complaint – and demanded he pay $10,000 for legal costs. Lochridge declined.

Then in July 2018, Oceangate sued Lochridge – and his wife Carole – for breach of contract, misappropriation of trade secrets, fraud and theft, amongst other allegations. The following month, Lochridge countersued for unfair dismissal.

Lochridge maintains that throughout the process OSHA was slow and failed to protect him from the ongoing retaliation he was receiving from Oceangate.

“I provided all the documentation to OSHA, I was on the phone to OSHA every few weeks.” he said. “OSHA did nothing.”

In December 2018, under increasing pressure from Oceangate’s lawyers, Lochridge and his wife took the decision to drop the case.

This meant the legal proceedings were settled, and as part of this agreement Lochridge withdrew his complaint at OSHA. OSHA stopped its investigation and also notified the US Coast guard that the complaint had been suspended. Lochridge also signed a non-disclosure agreement.

“Carole and I did everything we physically could, we just got to the point that we were completely burned… We had nothing left to give to it. They beat us down.”

Oceangate continued at pace with its plans to reach the Titanic.

In 2018 and 2019, the prototype sub made its first test dives in the Bahamas – including one, piloted by Stockton Rush, that reached a depth of 3,939m.

A crack was later found in the sub’s carbon fibre hull, and in 2020 that damaged hull was swapped out for a new one, in what became the second version of Titan.

In 2021, the company started taking passengers to the Titanic, and over the next two summers made 13 dives to the famous wreck.

But in June 2023, the sub went missing with five people on board – including Stockton Rush. After days of anxious waiting, the sub’s wreckage was found littered across the ocean floor.

At the US Coast Guard’s public hearings held last year, Lochridge criticised OSHA for its lack of action. “I believe that if OSHA had attempted to investigate the seriousness of the concerns I raised on multiple occasions, this tragedy may have been prevented.”

“It didn’t need to happen. It didn’t – and it should have been stopped.”

In response to Mr Lochridge, a spokesperson for OSHA said its whistleblower protection programme was limited to protecting individuals against employer retaliation. They said their investigation had “followed the normal process and timeline for a retaliation case”.

OSHA said it does not investigate whistleblowers’ underlying allegations about public safety… but instead refers those to the appropriate agency – in this case, the US Coast Guard.

The spokesperson said: “The Coast Guard, not OSHA, had jurisdiction to investigate Mr. Lochridge’s allegations regarding the safe design and construction of marine vessels.”

But the US Coast Guard’s report into the disaster agrees with Lochridge and says that OSHA’s slow handling of the investigation was a missed opportunity for early government intervention.

The report also criticises a lack of effective communication and coordination between OSHA and the USCG.

The investigation found that the email from OSHA to the coast guard about Mr Lochridge’s complaint was not received. It had been sent to a staff member who had responsibility for monitoring OSHA cases – but the employee had moved on to a new job within the agency.

Jason Neubauer, the chair of the USCG’s Marine Board of Investigation, told the BBC that the coast guard could have done more.

“The system did not work for the whistleblower in this case, and that’s why we just need to get better – and we have.”

Oceangate said that in the wake of the accident, it had permanently wound down operations and directed its resources towards cooperating with the inquiry.