The original was the biggest hit ever, but the sequel still took a long time to come together. How will it resonate in a different era of moviegoing?James Cameron knew the question I really wanted to ask about his new sequel, “Avatar: The Way of Water.”“‘What took you so long?’ Let’s not beat around the bush,” the director cracked.It’s a fair query, since after Cameron’s 2009 sci-fi adventure took in nearly $3 billion and became the highest-grossing film of all time, a follow-up that returned us to the beguiling alien world of Pandora was slow to materialize. Hollywood has changed so much in the interim that 20th Century Fox, the studio that financed “Avatar” and Cameron’s megahit “Titanic,” was acquired by Disney right after the sequel finally went into production in 2017.So what did take Cameron so long? On a recent video call with his cast, he confessed to blowing off the movie for a few years while indulging his passion for deep-sea exploration. After constructing a submarine designed to take him to the bottom of the Mariana Trench, the deepest-known place on this planet, Cameron accomplished that goal in March 2012, even as his “Avatar” actors fretted.“We kept thinking, ‘I hope he survives to make a new movie,’” Sigourney Weaver said.And even when Cameron convened a writers room to map out a second and third film, “I just wound up with more story than I bargained for,” he said. A tale that was initially conceived to complete a trilogy came to span four more movies, which all required a considerable amount of preproduction: Writing those new movies took four years, and designing their different biomes, cultures and wardrobes took an extra five.But “Avatar: The Way of Water” acknowledges that plenty of time has passed since the first film: In this installment, the soldier-turned-liberator Jake Sully (Sam Worthington) and his great love, the blue-skinned alien Neytiri (Zoe Saldaña), are parents to a brood that includes three Na’vi children, a human boy who becomes part of their coterie and an orphaned, teenage Na’vi played by the 73-year-old Weaver through the magic of motion capture. (This is a different character than the one Weaver played in the first “Avatar,” and one hopes that any potential confusion is mitigated by the casting decision’s irresistible boldness.)Worthington, right, with the director James Cameron on set. “You’ve got to have something that the actors can get their teeth into” Cameron said of the screenplay.20th Century Studios“Avatar: The Way of Water” also adds new co-stars like Cameron’s “Titanic” lead Kate Winslet, and incorporated several deep-sea sequences that required the cast to film underwater while holding their breath for minutes on end. “You always walk away after an ‘Avatar’ journey feeling like you know more than you did before, and that’s exhilarating,” Saldaña said.Do they feel pressure to replicate the stunning success of the first “Avatar”? “You can’t be a slave to the outside forces,” Worthington said. “You’ve just got to go to work and be fearless and as true as you can.” Still, Cameron is a realist: He has already shot the third film and a little bit of the fourth, but he knows that his ability to finish a five-film franchise hinges on the box office performance of “Avatar: The Way of Water,” due in theaters Dec. 16.“If we make some money with two and three,” Cameron said, referring to the sequels, “it’s all mapped out. Scripts are already written, everything’s designed. So just add water.”Here are edited excerpts from our conversation.It’s not easy to follow up making the highest grossing movie ever, but James, you’ve now had to do it twice. What did you learn from the aftermath of “Titanic” that could be applied as you follow up “Avatar”?The Return of ‘Avatar’The director James Cameron takes us back to the world of Pandora for the sequel “Avatar: The Way of Water.”What to Know: The sequel opens on Dec. 16, 13 years after “Avatar” shattered box office records. If you remember little about the original movie, here is a refresher.Holding Their Breath: Cameron and the sequel’s cast discussed what it took to get the new “Avatar” made and to bring it to life in a changed world.Back to the Theater: To help reacquaint audiences with the 3-D filmmaking that dazzled audiences in 2009, the first movie was rereleased in theaters on Sept. 23.From the Archives: Cameron “hasn’t changed cinema, but with blue people and pink blooms he has confirmed its wonder,” our critic wrote after the release of “Avatar” in 2009.JAMES CAMERON You can’t think in those terms. If I brought that into every decision I make, then it’s like, “OK, is the color that’s going to go on the back of this Ilu going to make the difference of $10 million global gross?” I have to remind myself constantly to just have fun and enjoy the day because otherwise you’re competing with yourself.So is this a more fun James Cameron?SAM WORTHINGTON Yeah, absolutely.CAMERON Don’t all speak at once.What was the biggest difference between making the first and second film?ZOE SALDAÑA There were many more challenges. I was younger in the first installment, I didn’t have children. Now I have three children.Zoe Saldaña as Neytiri. She learned to hold her breath underwater. “I come from generations of island people,” and on colonized islands “you are taught to love the ocean as if it’s a goddess, but you fear it.”20th Century StudiosCAMERON And Zoe and Sam now play parents, 15 years later. In the first movie, Sam’s character leaps off his flying creature and essentially changes the course of history as a result of this crazy, almost suicidal leap of faith. And Zoe’s character leaps off a limb and assumes there’s going to be some nice big leaves down there that can cushion her fall. But when you’re a parent, you don’t think that way. So for me, as a parent of five kids, I’m saying, “What happens when those characters mature and realize that they have a responsibility outside their own survival?”Did having children change the way you take risks in your own life?CAMERON Yes, I was pretty wild in my misspent youth, and there are a lot of risks that I wouldn’t take now. I see some of that wildness in my own kids, and there are stories that are embargoed until they’ve turned a certain age. But it definitely colors your whole perspective to have children.I also want to do the thing that other people aren’t doing. When I look at these big, spectacular films — I’m looking at you, Marvel and DC — it doesn’t matter how old the characters are, they all act like they’re in college. They have relationships, but they really don’t. They never hang up their spurs because of their kids. The things that really ground us and give us power, love, and a purpose? Those characters don’t experience it, and I think that’s not the way to make movies.WORTHINGTON Jim wrote this family in a great way where not only are the stakes life and death, but the conflicts are quite domestic. You’re still having these arguments with kids that you have every day, like, “Pick up your clothes, eat your food,” even though the world is at war. To be honest, I’ve used a lot of what I learned from reacting to teenage boys in the movie and put it back into my real life, because I’ve got three boys — it’s a zoo at my house — and someone’s got to be the Great Santini and keep them in line.James, even before you had kids, a lot of your action films explored that parental dynamic. I’m thinking of Sarah Connor and her son, John, in “Terminator 2,” or Ripley and Newt in “Aliens.”CAMERON I think it’s a question of what interests one as a writer and director. The one thing I’ve learned is that you’ve got to have something that the actors can get their teeth into, something that they can draw on from their life experience. I knew as I was writing it that Sam and Zoe were new parents and that this stuff would resonate for them, but if you’re speaking to a young audience, let them feel validated that kids on another planet, 200 years from now, are going through the same crap they’re going through right now.Sigourney, how did you react when you learned you’d be playing a moody, motion-captured 14-year-old?SIGOURNEY WEAVER I remember when Jim finally made the decision, he said, “You can do this because you’re so immature. Nobody knows this but me, but I know that you’re just 14 at heart.” And I think Jim is about 16, so he’s not off by much! But it was incredibly exciting to set loose your inner 14-year-old and to refine it, because being 14 is not all fun. I think we all remember how excruciating it can sometimes be and how unjust things seem in the moment. If you’re playing someone as sensitive as a 14-year-old girl who’s been uprooted, that’s a whole world of adventure you get to have as this character.Sigourney Weaver plays the teenage Kiri, left, in the new film as her character Dr. Grace Augustine, right, died in the original.20th Century StudiosZoe, what was it like to play the mother figure to Sigourney Weaver?SALDAÑA Oh my God, there were moments I would go, “There’s that teenager that just hates me.” I was a daughter before I became a mother, and I do remember those moments with my mom when I felt completely confused and misunderstood.Movies like “Aquaman” and the upcoming live-action version of “The Little Mermaid” take place underwater but don’t actually submerge the actors. “Avatar: The Way of Water” does, and the actors had to learn how to hold their breath for several minutes to shoot some of its undersea sequences. What’s gained from doing it for real?CAMERON Oh, I don’t know, maybe that it looks good? Come on! You want it to look like the people are underwater, so they need to be underwater. It’s not some gigantic leap — if you were making a western, you’d be out learning how to ride a horse. I knew Sam was a surfer, but Sig and Zoe and the others weren’t particularly ocean-oriented folks. So I was very specific about what would be required, and we got the world’s best breath-hold specialists to talk them through it.SALDAÑA The first step is you fake it till you make it: You tell your boss, “Yeah, absolutely, I’m so excited,” and then it’s complete horror, like, “What am I going to do?” At best, you’re going to walk away with a brand-new aptitude, but I was scared. I come from generations of island people, and the one thing people don’t know about island life is that if you’re from islands that have been colonized, a great percentage of people don’t know how to swim. Through folklore, you are taught to love the ocean as if it’s a goddess, but you fear it.When it came to holding your breath, what were your personal bests?SALDAÑA I’m very competitive, but we had an Oscar-winning actress in our cast that did seven minutes.Was that Kate Winslet?WEAVER Jesus, yeah, seven minutes.Did you have any idea she was capable of that?CAMERON No, and she didn’t either! But Kate’s a demon for prep, so she latched onto the free diving as something that she could build her character around. Kate’s character is someone who grew up underwater as an ocean-adapted Na’vi — they’re so physically different from the forest Na’vi, that we’d almost classify them as a subspecies. So she had to be utterly calm underwater, and it turned out that she was a natural.SALDAÑA I got almost up to five minutes. That’s a big accomplishment, you guys.CAMERON Five minutes is huge. Sig did six and a half.WEAVER To the surprise of the teacher! He said to get rid of your mammalian instinct to go, “Oh my God, my face is in the water.” So you spend several minutes just putting your body back into that element and letting those land-person feelings dissolve.SALDAÑA I was just in Europe, swimming in the Mediterranean with my husband and our children, and I passed it down to my boys — they were swimming underwater. I could do that because I surrendered to something, but it wasn’t wonderful from the beginning, I have to say.CAMERON Now it all comes pouring out.WORTHINGTON The trauma!Since the first film came out, environmental issues have become even more urgent. How does “Avatar: The Way of Water” speak to that?WORTHINGTON In the first movie, Jake Sully says, “Open your eyes. Sooner or later, you have to wake up.” That’s what he does in the movie — he wakes up to the world and this other culture — and I think that “Avatar: The Way of Water” is about protecting all of that.Neytiri and Jake Sully in the sequel. Now that they are parents, Cameron said, “what happens when those characters mature and realize that they have a responsibility outside their own survival?”20th Century StudiosCAMERON In the first film, you wind up with a sense of moral outrage about the destruction of a single tree. We have something very similar that takes place in “Avatar: The Way of Water,” and from what we’ve seen from test audiences, people feel that same sense of moral outrage. Does that translate in some tiny way when people come out of the theater into the way they think about the world, about nature, about our responsibility to the environment? Maybe, I don’t know.WEAVER You opened our eyes in the first one, but the second one, because it deals with the oceans and we’re having a crisis with the oceans, I feel it’s so much more transformative. If our goal is to become part of the World Surf League campaign and protect 30 percent of the ocean by 2030, I truly feel that this film is going to advance that goal. And it’s enhanced by the fact that the 3-D will absolutely put you on Pandora, in the water.CAMERON Jacques Cousteau said, “You won’t protect what you don’t love.” He knew that the way to get people to love the ocean is to show it to them with all its beauty and complexity and grandeur. We’re losing the whales, we’re losing the dolphins, we’re losing the sharks. We’re losing the coral reefs due to atmospheric [carbon dioxide] dissolving in the ocean. People will look back a hundred years from now and say, “We had all those things, and we squandered them.” So that’s in [the movie], but in a very organic way as part of the storytelling. The warning is between the lines.The first “Avatar” was a major breakthrough when it came to 3-D. What do you make of what happened to the format in the years after that?CAMERON I think the studios blew it. Just to save 20 percent of the authoring cost of the 3-D, they went with 3-D post-conversion, which takes it out of the hands of the filmmaker on the set and puts it into some postproduction process that yielded a poor result. I do think that the new “Avatar” film will rekindle an interest in natively authored 3-D, which is what I personally believe is the right way to do it. I say either do 3-D or don’t do 3-D, but don’t try to slap it on afterward to get the up-charge on the ticket.SALDAÑA And look, do you want to make a lot of money, or do you want to make something you’re truly proud of that stands the test of time?CAMERON Do I have to choose?SALDAÑA It’s unfortunate, but people chose the moneymaking machine, the post-conversion. And not every director is like Jim, with the level of commitment you put into it. That’s the difference between a project that is just a blockbuster hit and something that is truly special, and I wish more directors would understand that. If they just did a little course at the [Directors Guild of America] …CAMERON I’ll teach it! More