A scene from Sanctum, from left: Rhys Wakefield and Richard Roxburgh Image Credit: Rex Features

If you think your boss is intimidating, imagine how Alister Grierson feels.

The Australian filmmaker, who made his new movie, Sanctum, under the guiding hand of Avatar creator James Cameron, had to present a finished cut to the famously exacting director in Cameron's home theatre.

"Every time he'd twitch, I wondered, ‘Oh no, what did I do wrong?'" recalled Grierson, 41, who had previously directed only one other movie. "It was like sitting with God at the pearly gates watching your entire life."

Life and death are not quite at stake when Sanctum, a modestly budgeted ($30 million [Dh110.15 million]), 3D, cave-diving adventure comes out. But the movie is the lowest-budgeted feature that Cameron, who serves as its executive producer, has been involved with in more than 25 years, and it's an important test of his belief that 3D can be as effective in an intimate, emotional story as it is in a grand epic.

Sanctum essentially asks: Is the z-axis element enough to get the filmgoing public to embrace a movie in a well-worn genre with no well-known actors and few other obvious selling points?

The film tells the story of veteran cave diver Frank (Richard Roxburgh) and his alienated son Josh (Rhys Wakefield) who wind up, along with a larger diving team, trapped far below the surface when a freak storm hits during an expedition. As the dangers mount and claim the lives of many on the team, Frank and Josh must work through their issues if they are to survive.

Sanctum was conceived from the start in 3D, and shot to take full creative effect of the tool. Sanctum came together when Andrew Wight, a longtime Cameron friend and collaborator, decided to make a movie about a group of trapped cave divers using the same tools and techniques they deployed on Cameron's documentaries. Cameron agreed to godfather the film.

Cameron plays down his involvement. "I can't stop the studio marketing people from picking the path that they think is going to make the most money for the movie, but I would hope people would look past that," he said. "It's Andrew and Alister's film."

Father-son relationship

Still, even casual movie fans will recognise many of Cameron's visual signatures in Sanctum. While Cameron came to the set only once he helped develop the script and offered feedback in the editing room.

Cameron says that in addition to deploying his beloved gadgetry, Sanctum allowed him the chance to play with something else: a father-son relationship. "I haven't done [that] before," he said. "And as the father of two boys, I thought this could be interesting to explore."

For Wight, the story is even more personal. In 1988, while the producer was leading a cave dive in Australia, a storm like the one in the film trapped him and 14 others. The group survived, but only after two uncertain days spent trying to find a new way out. "I reflected on the personalities and the people and how they got together in that survival situation," Wight said. And I thought, ‘Boy, there's a fantastic film to be made out of that.'"

Cameron too is a diving enthusiast. Wight has helped Cameron go on half a dozen dives exploring various wrecks and deep-marine life while the pair filmed documentaries about them.

"We looked at our last expedition and said, ‘This is more complex logistically and technologically than a feature motion picture,'" Cameron said, describing the chain of ideas that led to Sanctum. So Cameron decided to do what he often does: combine a dive with a film shoot.

But Sanctum is not so much a labour of love for the filmmaker as it is a labour of purpose, a chance to show the world that 3D can be done well even when it's done for a smaller price.

"I wanted to demonstrate to the greater filmmaking community that you don't need to be making a $300-million film to do a world-class 3D film," Cameron said. "I was so tired of these stupid conversions being made and the idea being that 3D is too expensive. You can make a world-class 3D experience on a modest budget."

Watershed moment

Not that it was easy to do. Underwater movies tend to involve big set pieces, and big set pieces don't come cheap. To save money, Grierson was forced into some "MacGyver"-type solutions.

But even with all the technical achievements Grierson and his team pulled off, the question remains: Will filmgoers bite? Sanctum has no stars and traverses territory that has been explored in a number of other underwater adventures. Its biggest name, in fact, is Cameron.

Those who made Sanctum say they believe the movie turned out to be a, well, watershed moment.

"I'd like to think there may be a point in time that people will look back [on Sanctum] and say, ‘Hey, that film was significant in that it showed people there was a way forward for 3D,'" Wight said, adding, "3D is part of the next evolution of cinema, whether people want to admit to it or not."

Don't miss it!
Sanctum is released in cinemas across the UAE on Thursday.