For Avatar: The Way of Water, James Cameron and his team had to go back to blueprints and diagrams to figure out how to shoot a fantasy movie realistically underwater because no one had done it before.

”The key to it was to actually shoot underwater and at the surface of the water so people were swimming properly, getting out of the water properly, diving in properly,” Cameron says. “It looks real because the motion was real. And the emotion was real.”

For filming in the water, the film crew constructed a giant tank at Manhattan Beach Studios. It had enough capacity to allow the filmmakers to recreate the appearance of a real ocean, over 36 meters long, 18 meters wide, 9 meters deep, and held over 940,000 liters of water.

“Thanks to this, we could do waves breaking on the shore and have people trying to get out of the water while they’re getting hit by waves. We could create wave interaction with the creatures and people surfacing, getting hit by a wave and trying to say their lines and trying to breathe at the same time.” A system of propellers was used to move the water in the tank, which was called the “racetrack”. It consisted of two ship propellers with a diameter of 1.8 meters. “It was only a 10-knot current, but we were able to make it look much faster for the film,” Cameron says.

Interestingly, in order for motion capture technology to work underwater, the water must be very clean and transparent. So while Cameron originally planned for the crew to wear scuba gear during filming, the breathing apparatus created ripples and bubbles in the water.

“You can’t have a lot of air bubbles,” the filmmaker explains. “Every one of those air bubbles is a little wiggling mirror, and the system that’s trying to read all the marker dots on the actor’s body so it can capture their motion can’t tell the difference between a marker dot and a bubble.”

That left the only way out: “Everybody who was working in the tank was holding their breath,” Cameron says. “If there was somebody down their holding the light, they were holding their breath. If they were operating a camera, they’re holding their breath. The actors, of course, had to be holding their breath.”

To demonstrate convincing underwater acting, the actors additionally engaged in freediving with world-renowned expert Kirk Krack.

“The actors really enjoyed it,” says Cameron, noting that while every member of the ensemble proved adept at free diving, Winslet took to the water with astonishing ease. Says Cameron, “Kate enjoyed the freedom of being able to express herself underwater. She was able to do a static breath hold for something like 7 minutes and 20 seconds. I’ve been a free diver for 50 years, and I think the longest I’ve ever held my breath was 5 and a half minutes.”

Motion capture filming for Avatar: The Way of Water began in September 2017 and lasted approximately 18 months. During this period, Cameron and the cast worked on scenes for all four sequels.

“For the actors, it’s a very pure process,” says Cameron. “They’re not distracted by anything. We just roll. Sometimes we’ll record for 10 to 12 minutes straight.”

After Cameron and the editing team selected the best shots for each moment of a particular scene, the director used the revolutionary Virtual Camera to create specific shots. This Virtual Camera allowed the director to shoot scenes in his computer-generated world as if he were shooting on location. Through this Virtual Camera, the director would see not Zoe Saldaña, Sam Worthington or Sigourney Weaver, but their giant blue characters in the world of Pandora.

”While filming, I could see everybody where they’re supposed to be, above or below the water, and I could talk to them over the diver address system. They were acting to real-time direction based on what I was seeing on the virtual camera,” Cameron says.

After the shots shot on the Virtual Camera were edited in the right sequence, they were handled by the visual effects team of Wētā FX from New Zealand. Under the direction of Senior Visual Effects Supervisor Joe Letteri, a four-time Academy Award winner known for his groundbreaking work on Gollum and King Kong, Wētā FX worked to preserve the individuality of each character.

Academy Award winner Richard Baneham worked with Letteri on visual effects. Together, they helped the VFX artists be absolutely true to the actors’ work. Of course, the artists had to add subtle movements to the Na’vi’s tails and ears that the actors couldn’t do themselves. But even in such cases, the goal was always to stay close to what the cast put into their work. Letteri: “It was important for me to be with the characters, to see their actions, to understand what they feel and what they go through. That emotional connection is what you always strive for.” Cameron adds, “To us, integrity is very important — physical, emotional, face, eyes, everything. What the actor did at that moment is sacred.”

For Avatar, the visual effects team developed an “image-based facial expression capture” system using a special camera that was aimed directly at the actors’ faces and attached to the costume using a special device. This camera recorded facial expressions and muscle movements in detail like never before. Most importantly, the camera recorded eye movements, which was not the case with previous systems.

Working together with the Lightstorm team, Wētā FX not only had to create photorealistic characters that were attractive and emotional, but also the world of Pandora in digital form on a level never seen before. Every plant, every tree, every rock had to be created and rendered on the VFX team’s computers; a major breakthrough in lighting, shading, and rendering allowed them to create shots far more complex than ever before. Especially if you consider the omnipresence of water in the scenes. More than five years of research and development went into inventing new software and methodology to shoot the sequel.

“Not only does the film take place under and above the water, but a really big part of it is water shots,” says Cameron. “We needed to figure out how water moves, when a huge creature moves tons of water with its fin, or when the tiniest drop of rain falls on a person’s forehead, runs down the eyebrow and down the face. It’s an incredibly difficult question, but it’s not like we’re starting from scratch. We’ve been modeling water since on the Titanic, but we’ve taken it not just to the next level, but to five levels. The beauty of it is that if you can figure out water for this movie, you can shoot water anytime until the end of time. So these tools are becoming incredibly important to the effects industry in general.”

Thanks to James Cameron for the detailed comments for Mezha.Media. The movie Avatar: The Way of Water will premiere on December 6, 2022.