Forget green screen. The team behind Whalefall says the whale that swallows Austin Abrams' character was, for the most part, actually there.

A fresh trailer dropped this week for the survival thriller, based on Daniel Kraus' novel, and it puts Abrams inside the belly of a sperm whale with roughly an hour to get out before he runs out of air. There's also an angry squid down there, because apparently one monster wasn't enough.

The premise: a young scuba diver goes looking for his father's remains in the ocean and ends up swallowed whole. What could have played as pure CGI spectacle instead leaned hard on practical build, according to director Kristian Duffield, who co-wrote the script with Kraus and spoke to Empire about the shoot.

"Half of the whale's head, including its bottom jaw and mouth, was a big animatronic in a tank," Duffield said. He described a tongue puppet of sorts too, though not one that was actively puppeteered given how little room there was to work with inside the rig.

"Every trick in the book, we had at some point," he added. "Austin is physically in a whale mouth, there's no green screen in the water. He's really down there in a scuba suit, breathing real air, screaming, struggling, with jets of current shooting at him."

That's not a small ask for an actor. Duffield said Abrams handled nearly all the stunts himself, diving for real in a scuba suit while cameras rolled, and that the physical strain shows up on screen.

"Almost all the stunts in the movie are done by Austin," Duffield said. "It's always nerve-wracking when your actor is scuba diving and doing stunts. There was never a moment where he was remotely phoned-in. He could not have given more to this movie."

The cast around Abrams is stacked for a film this size. Elisabeth Shue, Josh Brolin, John Ortiz, Jane Levy and Emily Rudd round out the ensemble, though none of them are believed to be spending as much time submerged as the lead.

Whalefall opens in theatres on October 16. Whether the practical creature work translates into something that actually scares people, as opposed to just looking impressive in a trailer, is the thing audiences will settle in three weeks.

For now, the pitch is simple: a man, a whale, a squid, an hour. And apparently very little of it faked.