Titanic submersible crisis: Movie director James Cameron recounts the time he escaped catastrophe when his controls crashed during ultra-deep dive

The small deep-sea dive vehicle Titan has been out of communication with the surface of Earth since beginning its dive to the Titanic wreck, about 40 miles off the Canadian coast, on Sunday, June 18.

Onboard are British-Pakistani businesswoman Shahzada Dawood, his teenage son Suleman, British businessman Hamish Harding, ex-French navy commander Paul-Henri Nargeolet, and sub pilot Stockton Rush.

Their last position and depth is not known, however the wreck lies at about 12,500ft under the waves (where it had been discovered in 1985).

One of the most prominent adventurers to have undertaken such trips is Mr Cameron, who began diving to the shipwreck in advance of completing his 1997 blockbuster movie Titanic.

After the film, he continued embarking on such dives.

Here, in a 2013 interview with University of California Television, he tells of one such ill-fated excursion, revealing just some of the perils facing those who venture to the bottom of the ocean.

He described one trip with a target depth of –27,000ft, to the floor of the New Britain Trench, east of Papua New Guinea.

"I knew that I was going to be diving deeper than any other piloted submersible in the world, operationally right now, could go,” he said in the interview.

"And that it'd be a solo record, and that sort of thing.

"As I was going down and I think I was at around 26,000 feet, things started to fail on the sub, and it was one system after another after another, and I was trying to chase down what was happening.

"I couldn't tell if it was pressure related, or what was going on.

"I began to suspect that it was what they call the PAC – the control computer that all the systems ran through, that controlled everything by serial protocols up through just a small number of penetrators.

"And it was a little spooky because I lost my altimeter, I lost my depth gauge, I lost control of the lighting systems, I lost control of the propulsion and so on.

"And I was really debating if I should go on, and at a certain point I wound up releasing shot ballast because I didn't know where the bottom was, and I had no way of seeing it coming and I didn't want to crash into it.”

He managed to make it back to the surface, but without having seen the seabed as intended.

It turns out the culprit had been “one line of code that they [his mission crew] had written the night before, that I had asked them to do – so it was completely self-inflicted”.

This line of code instructed the computer to record snapshots of data in such a way that when they accumulated it crashed the entire computer.

As well as Titanic, Mr Cameron has directed The Abyss, The Terminator, Terminator 2, Aliens, and Avatar.

He was in Belfast in 2012 for a launch of a 3D reworking of Titanic.

By that time, he had visited the wreck of the Titanic some 33 times.

He told this reporter: “Those Irish hands did some pretty fantastic workmanship.

“As we explored the inside of Titanic we were able to find out for the first time about that specific craftsmanship – the way Titanic was fitted out.

"So much of the woodwork, goldplated giltwork, brasswork is all still there.

“The irony is that the Olympic came back here to Belfast, was broken down after 25 years of sterling service and no longer exists.

“The Titanic still exists. It’s gone from our surface world, but it still exists as a kind of time capsule down there on the sea floor.

“The images we were able to bring back from the interior really are a tribute to the fine craftsmanship and workmanship of a ship that was built here, in Belfast...

“It’s been a great privilege for John and I to walk the grounds here where the ship was created. It’s been a remarkable, remarkable experience.”

• WATCH: Previously unseen footage released showing the first time human eyes caught sight of the wreck of HMS Titanic