Newly released footage from the US Coast Guard's investigation reveals the harrowing moment when Oceangate's submersible was lost during its fatal dive to the Titanic wreck in June 2023. The video, featured in the BBC documentary Implosion: The Titanic Sub Disaster, shows Wendy Rush, wife of Titan CEO Stockton Rush, hearing the unmistakable sound of the sub's catastrophic implosion and asking quietly: "What was that bang?"

The Titan, a private submersible built to dive nearly 4,000 metres to the Titanic wreck, imploded about 90 minutes into its descent, killing all five people on board instantly. Among the passengers were Mr Rush, British explorer , French diver Paul Henri Nargeolet, and British-Pakistani businessman Shahzada Dawood with his 19-year-old son Suleman. The group had paid for the experience to visit the Titanic's remains on the ocean floor.

The footage shows Mrs Rush sitting on the support ship, monitoring communications with the sub. When the implosion occurred at about 3,300 metres depth, a loud bang was heard.

Confused, she asks the crew members what the noise was, then receives a text from Titan saying it had dropped weights - a standard part of the dive process.

Tragically, this message was sent just before the implosion but took longer to arrive than the sound of the failure itself. The US Coast Guard investigation has confirmed that the "bang" was the sound of the Titan's hull collapsing.

The documentary reveals that Titan's hull was made primarily of carbon fibre mixed with resin - an unusual and risky choice for deep-sea submersible.

Carbon fibre's layers can separate under extreme pressure, a process called delamination. Evidence shows the hull had begun to break down a year before the disaster, during dive number 80.

Passengers at the time heard a similar loud noise, but the CEO dismissed it as the sub shifting in its frame.

Lieutenant Commander Katie Williams of the US Coast Guard said: "Delamination at dive 80 was the beginning of the end. Everyone who stepped onboard the Titan after dive 80 was risking their life."

Despite these warning signs, Titan completed three more dives in 2022 before the fatal dive in June 2023.

The wreckage of the submersible was found scattered across the Atlantic seabed, with personal effects such as Mr Rush's clothing and Titanic memorabilia recovered from the debris.

Several experts and former employees had warned about the safety risks of Titan's design, describing it as an "abomination" and predicting disaster

Deep-sea explorer Victor Vescovo said he warned people not to use Titan and told Stockton Rush the sub would fail catastrophically.

Businessman Oisin Fanning, who took two dives before the tragedy, told the BBC he would never get back in the sub knowing what he knows now.

Christine Dawood, who lost her husband and son in the implosion, spoke about the lasting trauma in the documentary: "I don't think that anybody who goes through loss and such a trauma can ever be the same."

An Oceangate statement provided to the BBC said: "Oceangate told the BBC: "We again offer our deepest condolences to the families of those who died on June 18, 2023, and to all those impacted by the tragic accident.

"Since the tragedy occurred, Oceangate permanently wound down its operations and focused its resources on fully cooperating with the investigations. It would be inappropriate to respond further while we await the agencies' reports."

The US Coast Guard's Marine Board of Investigation is expected to release a final report later this year, aiming to uncover exactly what went wrong and prevent future disasters of this kind.