James Cameron brings Titanic back in 3D – but is it just the tip of the iceberg?

When Titanic became the most profitable movie ever, generating $1.8 billion at the box office globally in 1997, director James Cameron claimed to be pleasantly surprised. It was, he joked, an unlikely triumph for a three-hour "chick-flick" to which everyone already knows the ending.

In a few months' time, Cameron will bring Titanic back to cinemas. It will remain three hours long, with the same tissue-drenching plot twists, and a denouement which surprises nobody. But this time, one big thing is different: audiences will be able to watch that very large ship sink in three dimensions.

On Wednesday, Cameron unveiled 18 minutes of his 3D remake to the media at Fox Studios in Los Angeles. A team of 300 technicians is spending 60 weeks converting the original, painstakingly cutting out objects on screen and pushing some to the foreground, some to the back. The work will cost $18m (£11m).

"This is not about the money," Cameron said. "This is about giving people an opportunity to see Titanic in movie theatres again."

The project is at the cutting edge of Hollywood's latest trend. Thanks to the advent of 3D technology, film studios have suddenly realised that they can make new money from old ideas, by converting classic movies from their back catalogues into the new format, and putting them in cinemas once more.

In September, Disney tentatively released a 3D remake of The Lion King. It shot straight to the top of the box office charts, outperforming a swathe of original new titles and making (so far) some $93m in the US alone. Most of that was straight profit.

A host of copycat projects are duly in the offing. Early next year, George Lucas will bring the first of his Star Wars films back to theatres in 3D. A 3D version of Top Gun will follow soon afterwards. Pixar's Monsters Inc and Finding Nemo are already being converted, and there are rumours that Indiana Jones will soon be cracking a whip in three dimensions in Raiders of the Lost Ark.

To the film industry, re-formatting classics looks increasingly like a commercial no-brainer: in the past two years the cost of converting to 3D has fallen from around $100,000 per minute of film to nearer $25,000, while every indication suggests that the public will pay handsomely to see old favourites which have been re-rendered.

Like most success stories, in an industry where art and finance collide, 3D conversion is not without critics. Spiralling costs, flat box office revenues, and falling DVD sales have in recent years seen a collapse in the number of original titles finding their way into cinemas (this year's top 10 contains just one film, Bridesmaids, which isn't either a sequel or an adaptation). Filling theatres with repurposed classics will, the critics argue, only add to that creative decline.

Film historians, meanwhile, say retro-fitting an old title for the 3D era is like slapping a fresh coat of paint on the Mona Lisa. "Does this threaten the integrity of a work? Of course it does," complains Wheeler Winston Dixon, the Ryan Professor of Film Studies at the University of Nebraska. "People are hungry for fresh content, and instead they are being given spectacle. This 3D thing is a gimmick being driven by tech-heads." But Cameron is adamant that there has never been a better time for the world to see Titanic. April, when the film is tentatively due to hit cinemas, marks the 100th anniversary of the ship's sinking. And everything from the 2008 credit crunch to the onward march of climate change make his movie's themes more relevant now than ever before.

"There's something enduring about the Titanic story," he claims. "You've got this basic arrogance that they could take this ship with over 2,000 people on board at full steam through a known ice field. At the time, they said their ship could never sink, because it was too big to fail. Now where've we heard that before?"

When The Independent raised criticisms of 3D reformatting, Cameron replied: "What's wrong with commerce? What's wrong with making jobs for people in movie theatres around the world? What's wrong with entertaining people? It's commerce, baby. It's art and business put together, and I have no problem with that whatsoever."

Sceptics, he added, are motivated by a mixture of cynicism and jealousy. "If you could wave a magic wand and give everybody in the world an orgasm simultaneously, there'd still be people looking for a way to criticise that."