Twenty-five years after the release of Titanic, Kate Winslet is starring in her second James Cameron film, Avatar: The Way of Water.

The long-awaited sequel sees the return of the Resources Development Administration to Pandora. This time around, they're not just after unobtainium. The RDA wants to colonize the entire moon. But, someone's standing in their way, Sam Worthington's Jake Sully. When Jake comes to learn that the RDA and a recombinant version of Colonel Miles Quaritch (Stephen Lang) have specifically targeted him, he decides that it's best for the Sully family to leave the forests of the Omaticaya clan.

Jake, Neytiri (Zoe Saldaña), and their four children head to the seas of the Metkayina clan and that's where they meet Winslet's character, Ronal. Ronal and Cliff Curtis' Tonowari are the leaders of the Metkayina. While Tonowari is a bit more open-minded about upholding the Na’vi tradition of granting safe harbor to any refugee seeking sanctuary, Ronal is far more reluctant to accept the Sullys and have them put her people at risk.

Why exactly is Ronal more resistant to taking in outsiders than her partner? I asked Winslet just that during our interview ahead of The Way of Water's December 16th release. Here's what she said:

"I think what I felt was very important to convey is the sense that Ronal is absolutely the matriarch. She is the leader of her clan, and I think she will stop at nothing to protect that and to protect what they have created. They really care for and look after not just their family, but that entire village, that entire community, the Metkayina clan. So the idea that anything from the outside could pose any sort of threat is something that I think, as a mother, she just instinctively feels and feels very wary of. She loves her little tribe. She loves her family. She wants them to have their freedom and not be, in any way, I suppose, restricted or possibly threatened. It was important to me to really play that side of her."

As for Tonowari, Winslet took a moment to sing the praises of the actor behind the Olo’eyktan of the Metkayina clan, Cliff Curtis:

"Cliff is just wonderful. I think he and I both wanted to play these parts because of these characters' commitments to family. He's very much a family man, and that sense of community, and his Maori heritage was something that he really, I felt, both consciously and subconsciously was able to bring into this role. Tonowari is such a powerful figure, and I feel that Cliff brings that as an actor. And he's very warm and very inclusive and kind."

Winslet also addressed the underwater performance capture experience, a type of performance she dubbed "the most pure form of acting." She explained:

"In many ways, motion capture, it's almost the most pure form of acting, and people wouldn't really think that because you don't see us as real people. You see the blue version of us as actors. But in order to capture that, you have cameras watching you from every angle. You also have a helmet and a helmet cam that is capturing every single muscle and movement in your face, so you can't hide. Even your eyeballs, the movement of your eyeballs is captured. And so in terms of performance, you really have to deliver because you want that camera to see every single thing that you're doing because you want as much of your facial muscles to be repeated in your Na'vi version of yourself. So it's quite an intense, demanding experience, but I absolutely loved it."

An intense, demanding experience, but not one without a little fun. Some of Winslet's youngest co-stars, namely Trinity Jo-Li Bliss who was just seven years old when filming began, instituted a swear jar. Slip and use a swear word? Money for the jar! What was the word that cost Winslet the most money? Here's what she said:

"Well, it's a word that begins with ‘F.’ And yes, I was the one who got in the most trouble. Trinity would be regularly, 'Kate! That's $5!' Yeah, I got in a lot of trouble most days and was very out of pocket because of the swear jar."

Avatar: The Way of Water premieres exclusively in theaters on December 16th. For more about the making of the movie, check out my interview with James Cameron below: