The final picture of British-Pakistani businessman Shahzada Dawood and his son Suleman has emerged in which they are seen smiling arm in arm before they boarded the doomed Titan submarine, Daily Mail reported.

Shahzada Dawood, 58, and his 19-year-old son Suleman boarded the submersible on the $250,000 per person trip in which they and three others perished.

Shahzada’s wife Christine revealed the pair spent their final moments listening to their favourite music in total darkness to conserve power while watching bioluminescent creatures in the deep before the Titan imploded.

She said that they arrived on the mothership at the harbour in St John’s, Newfoundland, in the middle of the night of June 15, and set sail for the dive site. There were briefings at 7am and 7pm, with scientific talks and discussion about the wreckage and the expedition, she added.

Christine said those preparing to make the descent were told to wear thick socks and a hat as it could get cold at the depths, and stick to a ‘low-residue diet’ the day before the dive, including not drinking any coffee the morning beforehand.

There was no toilet on board, and only a bottle or camp-style toilet behind a curtain.

The passengers were told to load up their favourite music onto their phones, to play via a Bluetooth speaker.

He also warned them that the descent would be in pitch black because the headlights were turned off to save battery power for when they made it down to the sea bed. They were told they would likely see bioluminescent creatures.

She described how she and her daughter Alina, 17, were on board the submersible’s mothership, Polar Prince, and waved her husband and son off on the adventure.

Three months earlier, OceanGate chief executive Stockton Rush and his wife Wendy had flown from the US to meet the Dawoods in London to convince the family it would be safe to travel to the wreck of the Titanic in his mini-sub despite concerns about its safety, she said.

Rush, who believed going to the depths of the Atlantic in the Titan was “safer than crossing the street”, met with the family at a cafe close to Waterloo in February to personally talk to them about the design and safety of the submersible.

Christine told The New York Times that “that engineering side, we just had no idea. I mean, you sit in a plane without knowing how the engine works”.

The family led by Dawood set off on the doomed trip 12 weeks later.

They flew to Toronto on June 14 but their flight to St John’s to join the expedition was cancelled. Their flight the following day was then delayed and they feared they might not make it to the Titan at all.

“We were actually quite worried, like, oh my God, what if they cancel that flight as well? In hindsight, obviously, I wish they did,” she said.

The Titan began its dive into the Titanic wreckage at 8am on June 18. One hour and 45 minutes into the dive, at 9:45am, contact was lost. The US Navy registered the sound of an implosion at that point. Five days later, debris from the sub was found on the sea bed, 1,600 feet from the Titanic.

The CEO of the company behind the expedition, Stockton Rush, 61; French Titanic expert Paul Henry Nargeolet, 77; 58-year-old British billionaire adventurer Hamish Harding; and Dawood and Suleman were likely to have been killed instantly.