Avatar 2 was so expensive to make that it has to earn $2 billion at the box office to break even

If you ask James Cameron how expensive Avatar: The Way of Water has been to make, you'll get a very blunt response.

"Very f**king [expensive]," he explained to GQ.

There's no denying there is a lot of hype about the upcoming sequel that has been more than a decade in the making.

But he'll be hoping plenty of people go to see the film as a lot is riding on it.

While Cameron is remaining tight-lipped about the true cost of the entire project, he did reveal that the CGI-filled flick was the 'the worst business case in movie history' when pitching it to studios.

In order for the film to make a profit, he told GQ that the movie has to become 'the third or fourth highest-grossing film in history' to even break even.

Yep, that's the threshold.

So we're expecting big things from Cameron's first movie in 13 years.

According to Variety, Cameron's original Avatar film is the highest-grossing movie worldwide with USD$2.9 billion (AUD$4.3 billion, £2.4 billion).

Avengers: Endgame comes in second place at USD$2.7 billion (AUD$4 billion, £2.2 billion).

Another Cameron film comes in at number three - Titanic, if you're interested - with USD$2.1 billion (AUD$3.1 billion, £1.7 billion).

Basically, if the studio wants to make any moolah off this movie it has to beat Star Wars: The Force Awakens, which made $2.07 billion (AUD$3.13 billion, £1.74 billion) and Avengers: Infinity War, at $2.05 billion (AUD$3.10 billion, £1.72 billion).

20th Century Studios/Album/Alamy.

The above prices are all unadjusted for inflation.

Only five movies in history have ever managed to rake in over $2 billion (AUD$3.02 billion, £1.6 billion) mark worldwide, so while he's got a task ahead of him, Cameron's lofty goal is achievable.

The sequel has been a long time coming since the 2009 hit original, but Cameron revealed to Entertainment Weekly that the sequel to the blockbuster has been in the works since 2012.

That being said, filming didn't actually kick off until 2017.

The film is aptly set around 14 years after the original, and its synopsis reads: "[Former human] Jake Sully lives with his newfound family formed on the planet of Pandora. Once a familiar threat returns to finish what was previously started, Jake must work with Neytiri and the army of the Na'vi race to protect their planet."

20th Century Studios

Cameron explained that the biggest challenge in making the film came from the fact that it's set underwater, which, as you can imagine, made its creation a lot harder.

In fact, a specially built 900,000-gallon tank was required for filming - but the producers will be getting their money's worth as it's also being used for the third and fourth films in the franchise too.

It's been a long wait for the second film, and the ones that follow, but we won't have to wait much longer.

Avatar: The Way of Water opens in theatres December 16.