Having become the highest-grossing Worlds of DC movie to date, Aquaman has now crossed the $1 billion mark at the worldwide box office.

Those are uncharted waters for a DC movie since The Dark Knight Rises in 2012 and marks a potential turning point for the troubled Worlds of DC. Marvel has had no trouble passing the milestone – six billion-dollar movies and counting – and DC will be hoping Aquaman's success transfers to Shazam! in March.

Cast your mind back a few months, though, and no one would have predicted Aquaman doing nearly as well as it has. The fishboy also known as Arthur Curry's brief, uninspiring role in Justice League didn't lead to much hype around his solo movie, especially as Justice League underperformed at the box office, making it the lowest-grossing Worlds of DC movie so far.

So just how did Aquaman end up becoming the first Worlds of DC movie to hit $1 billion at the box office?

1. China

VCG Getty Images

Almost a third of Aquaman's entire box-office haul has come from an incredible take in China, where it has grossed $282.8m as of January 6.

That's the best result (by far) for the Worlds of DC in China and makes it the second highest-grossing superhero movie of all time, behind only Avengers: Infinity War. Warner Bros seemed to know they could be on to a winner in the market as China received an early release of December 7, ahead of even the worldwide review embargo.

It's rare for China to get a big Hollywood offering before the US, so that definitely generated excitement for its release, helped by the fact that its early reactions were so positive. Capitalising on the excitement, Warner Bros gave it a big press push with director James Wan and stars Jason Momoa and Amber Heard in attendance.

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Talking of Wan, his presence can't be underestimated either. The director has had success in China before (Fast & Furious 7 took a $390.9m gross there) and would be a draw for Chinese audiences. Some outlets have speculated that the audience also responded to Wan's ethnicity (he is an Australian national of Malaysian Chinese descent).

"You have to add the fact that James Wan is an esteemed director. He's got credit for that. He's definitely a well-liked director in the market," Warner Bros's head of international distribution Tom Molter told Variety.

And if all that weren't enough, Aquaman also shared similarities with local smash hit The Mermaid, the fourth-biggest movie of all time in China. That movie was a fantasy rom-com about a businessman who falls in love with a mermaid assassin, so not exactly a match plot-wise, but definitely a similar aquatic world to that which appealed to Chinese audiences.

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2. It's actually quite good

Before Aquaman ended up doing so well at the box office, perhaps the biggest surprise was that it turned out to be quite a good movie, so that always helps.

Sure, it's not perfect, but there's a clear vision to the film, boosted by great leading turns from Jason Momoa and Amber Heard, as well as excellent action set pieces.

But it's still not as well-regarded as Wonder Woman among the critics and that movie 'only' grossed $821.8m worldwide.

Warner Bros.

So while the fact that Aquaman turned out better than even the most ardent DC fan hoped, its quality is not solely responsible for its box-office success – although it would help with repeat viewings.

3. Worlds of DC connection

Or rather, the lack of one. Aquaman features only one line of dialogue that ties it to Justice League – mentioning Steppenwolf of all the characters – and the wider Worlds of DC.

Instead, Wan rightly concentrated on the solo outing being a successful movie in its own right, rather than concerning itself with shoehorning in DC references or world-building for future outings.

The fact it was largely set in Atlantis also immediately set it apart from the likes of Batman v Superman and Justice League. Not only did this mean the movie could appeal to an audience who hadn't seen any Worlds of DC movies to date, it also meant jaded DC fans could be tempted back with the promise of something genuinely different.

4. Jason Momoa

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Even though Aquaman's Justice League showing wasn't great, the criticism was that the movie didn't give Jason Momoa's superhero enough to do, not that his performance was bad.

With his Game of Thrones background and (usually) fun press appearances, Momoa is a popular enough actor to be able ride out the Justice League negativity. It meant that people were keen to see what he could do with a bigger role and he succeeded, helped by Aquaman (rightly) giving him a much bigger arc and more depth.

5. Release date

After its early release in China, Aquaman was released around the world in the couple of weeks leading up to Christmas, including December 12 in the UK and December 21 in the US, with an Australian release on December 26.

Without a Star Wars movie to compete with, it was the only blockbuster action movie in the market until Bumblebee arrived, with the festive season's other big offering – Mary Poppins Returns – catering to a different audience.

Disney

While it's hard to judge without polling every cinema audience member, there's a chance that it looked the best prospect for a Christmas movie outing, especially with its decent reviews.

With a teen-friendly rating, Aquaman was also in the prime position to capitalise on the school holidays – and it clearly took full advantage around the world.

Aquaman is in cinemas now.

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