Behind-the-scenes photos from the set of James Cameron's Avatar sequels show how the director is taking the franchise underwater for its next chapter.The official Avatar Twitter account posted the shots and showed Cameron directing the actors for an underwater sequence. The tweet also explained that the floating white balls on the surface of the water are to prevent light from above interfering with filming.RELATED: Sigourney Weaver Returns to Avatar Sequels in BTS Photo

Prior to being placed on hiatus due to the coronavirus (COVID-19) outbreak, filming had been taking place in New Zeland as the Avatar sequel headed toward its December 2021 release. Although the sequel and Avatar 3 have reportedly finished filming principal photography, there is still a lot of work to be done. It was no secret that the series is moving from the treetops of Pandora into the moon's oceans next, but the photos provide a glimpse at how it was done.

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Cameron is no stranger to filming on the water, thanks to his work on The Abyss and Titanic, as well as the fact that he is a keen deep-sea diver. The underwater photos go hand-in-hand with concept art from the sequels revealed a whole host of nautical locations coming to the franchise's future. The original Avatar was praised for its groundbreaking visual effects and use of 3D, and despite the coronavirus lockdown, producer John Landau has confirmed "virtual" production is continuing on the movies. Given the scale of Avatar's CGI work, it means work can continue where many movies have been forced to  shut down completely.

Despite a lengthy wait between Avatar and its sequels, Cameron is taking a slow approach to marketing Avatar 2. The latest behind-the-scenes photos come months after images teasing a fiery action scene involving water and green screen technology.

With scripts reportedly finished and performance capture completed until Avatar 4, Cameron has been busy on more than just filming underwater sequences. It is evident that the scope of Avatar 2 will be greater than its predecessor, which is in line with Cameron's previous comments about why there is such a delay between movies. Speaking at Avatar's 10th anniversary, the director has previously explained the sequels are actually on schedule.

Written and directed by James Cameron, Avatar 2 stars Sam Worthington, Zoe Saldana, Sigourney Weaver, Stephen Lang, Giovanni Ribisi, Joel David Moore, Edie Falco, Kate Winslet, Oona Chaplin, Vin Diesel, Michelle Yeoh and David Thewlis. The film is slated to release Dec. 17, 2021, followed by Avatar 3 in Dec. 2023, Avatar 4 in Dec. 2025, and Avatar 5 in Dec. 2027.