Zoe Saldaña has a message for moviegoers ahead of the release of “Avatar 2” this December: “It’s definitely a leap from the first ‘Avatar,’ so you have to brace yourself for it. It’s going to be an adventure you wont forget.” James Cameron has spent well over a decade developing the sequel to his record-breaking “Avatar,” which will once again star Saldaña and Sam Worthington.

“I can get choked up just talking about it,” Saldaña told reporter Kevin McCarthy (via People) about the “Avatar” sequel. “I was able to see just 20 minutes of the second installment, right before the year ended, last year. And I was speechless. I was moved to tears.”

Not much is known about “Avatar 2” other than it centering on the children of Worthington and Saldaña’s characters from the original film. The movie will also explore the underwater worlds of Pandora, which is part of the reason it took so long to get made, as Cameron had to advance technology in order to record motion capture underwater. New cast members include Cameron’s “Titanic” star Kate Winslet, who held her breath for nearly 8 minutes while filming in a water tank.

“Jim was finally able to crack that challenge — that whole thing that you can’t imitate water, virtually, through performance capture,” Saldaña said. “That was just a challenge that he had taken upon himself, and it took him years, and he did it. He did it. It’s powerful, it’s compelling.”

“He’s also a big crier,” the actor added about her director. “He does have a very delicate heart, which is why he protects it so much.  And I think that he’s able to have an outlet through the stories that he creates.”

“Avatar 2” is set for release on December 16.