Action blockbusters, especially the ones with superheroes in them, have given audiences all kinds of battles in all kinds of locations. We’ve seen heroes fight villains in cities, alien planets, space, elevators, and almost everywhere in between. Aquaman director James Wan, however, has a unique opportunity to dazzle audiences with epic action in a fresh environment, under the sea.

Superhero News and a few other outlets visited Wan in the Aquaman edit bay last month where he showed us about 25 minutes of the film. One of the sequences featured a “Round 1” battle between Aquaman/Arthur Curry (Jason Momoa) and Orm (Patrick Wilson). Before the physical confrontation, Arthur talks trash while Orm offers his half-brother one last chance to back down and not interfere with Orm’s plans to wage war on the surface world. You can probably guess how receptive Arthur is to Orm’s offer.

The two Atlanteans ascend into an arena where they fight in front of the people over whom the winner will rule. What follows is an action sequence unlike any previously offered in any movie of any genre. Firsts are rare, but Wan finds one as Aquaman and Orm go blow-for-blow deep in the ocean, over a lava pit.

Atlanteans are powerful enough to move through the water at high speed, which creates unique offensive opportunities, but also a different set of dangers. Orm knows this better than Arthur, still a relative newbie in all of this, and has the home-field advantage. Both warriors impress, but Mera (Amber Heard) steals the show with the coolest use of super powers in this scene.

Creating something for which there is no previous template has obviously been challenging for Wan and the entire Aquaman team. A lot of research and development went into the film. “We wanted to make sure that things [look] somewhat authentic underwater as well,” Wan says. “We would build costumes, sets, and our actors, we would literally submerge them underwater and we did so much study just to see what they would look like.”

Submerging Momoa and his castmates led Wan and the visual effects team to an important realization. “The most surprising thing that we discovered very early on is people, objects, and stuff do not look wet underwater,” he says. “It only looks wet when you take it out of water, right? When it’s glistening and it’s dripping wet that’s how something looks wet. But when you’re underwater, it actually looks matte and so that concept was a bit tricky for us to kind of wrap our head around.”

The need to recreate that matte look gave Wan a new enemy in performer perspiration. “We’d constantly have to go in there and pat out actors down, like with makeup. Under those bright lights and all the stunts, they were constantly sweating and all that and you don’t see water underwater. You don’t see sweat, right?”

Giving the actors and props the right look was only part of the challenge. There was also the need to give the visual effects department something to work off of so that the characters could move properly. “We want to shoot as much [we can],” he says, “because even if visual effects was to come in and augment a lot of it, right? They want to start with something that is real, that’s tangible, that they kind of go see and can go ‘Oh this is what would happen.’”

Wan continues, “More importantly, it’s how the actors and the stunt actors would react and act and so that was really important. And then in postproduction, we try to take it ten notches up and make it even cooler, as much as we can.”

The process of creating these sequences will continue as the visual effects department tries to perfect each and every shot. The results are already impressive, though, as the battle between Arthur and Orm felt like Aquaman‘s first-of-its-kind potential was being unlocked before our very eyes.

Moviegoers are going to have a brand new experience when Aquaman hits theaters December 21.