LOS ANGELES (AP) — It was dawn on the set of "Blade Runner 2049" and Harrison Ford and director Denis Villeneuve were swimming back to the shore together after an all-night shoot in a million-gallon water tank.

It was cold in the water. It was cold outside. And it was just one night out of a dozen that they'd be spending their sleeping hours soaking wet to try to execute a set piece that even Ridley Scott thought too ambitious.

"What we are doing now is insane," Ford told Villeneuve. "It's insane."

He might as well have been talking about the whole project, which is, by one metric, a $150 million art house sequel to a 35-year-old sci-fi film that flopped on release. In 1982, Ridley Scott's neo-noir dystopian mind-bender based on Philip K. Dick's story "Do Androids Dream of Electric Sheep?" made a mere $27.6 million on a $28 million budget. For comparison, the year's top film, "E.T.: The Extra Terrestrial" made $359.2 million.

During the troubled production, Ford and Scott famously disagreed on even the nature of Ford's character Rick Deckard and whether or not he was a "Replicant" (aka an android), and neither liked the theatrical release which included a tacked on happy ending and a forced voiceover narration. Then came all those other versions. Seven are said to exist, five are still available. Both Ford and Villeneuve like "The Final Cut," from 2007, best.

And yet "Blade Runner" not only survived those rocky origins but transcended them to become a widely regarded sci-fi classic.

Still, the prospect for a sequel seemed dubious at best, especially when one of the primary rights holders nixed any attempt to start a franchise, fearful that someone might attempt to remake "Blade Runner." It took the late producer Bud Yorkin and his wife Cynthia Sikes 12 years to persuade him otherwise.

"I had this notion that there was an answer for a relevant sequel," Ridley Scott told the AP earlier this year. "Not just grunge and gloom and rain and dark, but a real story."

Scott worked for nearly two years on the story with Hampton Fancher and Michael Green with the intention to direct, but instead diverted his attentions to "Alien: Covenant." The producers from Alcon Entertainment then approached Denis Villeneuve, who they'd worked with on "Prisoners," and who would later gain an Oscar nomination for "Arrival."

With Ridley Scott's blessing, the promise of total creative freedom, Ford set to reprise his role and Ryan Gosling on board to co-star as a new LAPD officer, Villeneuve agreed to do it and set off on the "mad" task of making a worthy sequel to "Blade Runner." He had legendary cinematographer Roger Deakins at his side from "day zero" helping to craft the look and feel of the film from the storyboard stage on.

What exactly that story is, though, the producers and filmmakers hope will remain a secret until general audiences are able to see it for themselves — one of those "everything is a spoiler" films that they believe is best seen with uninformed eyes.

Shooting took place in Budapest (for space and financial reasons), so gone are the Los Angeles landmarks that helped define the original — the Bradbury Building, the Ennis House, Union Station and so on — and in its place are brutalist Soviet-era structures and massive sets that even Ford marveled at to represent what Los Angeles might look like in 2049.

And then of course there was that gigantic water tank that took two months to build.

"It was by far the biggest technical challenge of my life and at the same time, I had fun like a kid. I will say we went through it and it went very well," Villeneuve said. "Both of my main actors were gentlemen. They were troopers. Never complained. Harrison was always the first one in the water. To see that man, that legend who is no spring chicken being out at 4 a.m. in the water with a big smile? It warms everybody's heart."

Ford said he knew on set that he was making something special.

"We were there, we saw what was going on and thought that it was going to be good," Ford said. "It's just epic."

The completed film, he added, will "knock your socks off."

Early reviews mostly agree. The film currently boasts a "Fresh" 96 percent on Rotten Tomatoes and is tracking for a debut in the $40 million range — which could rise with good word of mouth. It's no secret to say that Alcon, which co-financed with Sony, needs the film to be a hit. The company has virtual reality tie-ins planned and knows that there is a whole universe to be mined in the "Blade Runner" mythology, including prequels and off-world adventures.

"Sometime in the next 35 years we'll probably do something," Alcon co-CEO Andrew Kosove said with a smirk. "It's tricky. We do have business decisions to think about, but this is a unique circumstance. It's not Marvel. It's not DC. There's got to be a real reason to do it, otherwise it won't work commercially anyway."

Villeneuve, for his part, is at peace with the film.

"I'm not saying the movie is perfect, but I'm saying that there is something there that is part of my initial dream. How the world will react I have no idea," he said. "I always make movies like they are my last ones. You never know what will come next. I gave it everything for better or worse. It verges on insanity to do that but I'm calm and you know why I'm calm? Harrison Ford loved the film. And Ridley Scott, too. For me, to know that both fathers gave their blessing, I feel OK."