See Charlize Theron go to extremes in exclusive 'Apex' trailer

All those times she climbed trees barefoot growing up in Africa are finally paying off for Charlize Theron.

The Oscar winner known for her action-movie mettle goes to new extremes for “Apex” (streaming April 24 on Netflix). USA TODAY exclusively unveils the trailer for the upcoming survival thriller, directed by Baltasar Kormákur (“Everest”) and also starring Taron Egerton and Eric Bana.

Sasha (Theron), an expert rock climber, heads to the wilds of Australia to grieve and find solace after the tragic loss of a loved one. Smiley, jerky-peddling local Ben (Egerton) is one of the nicer dudes she meets, though Sasha just wants to be by herself in nature.

When her gear is stolen, Sasha runs into Ben again but quickly discovers the truth: The guy is actually a sadistic serial killer who hunts his prey with a crossbow, leading to a death-defying chase involving raging rapids, dangerous cliff jumps and treacherous rock climbing.

"I remember reading it and it really, truly propelling me into this kind of vortex, and I was interested," Theron says of the script. The characters were “complex” and she “saw so much potential.” She also enjoyed how, “out of necessity,” the dynamic between Sasha and Ben evolved from foes to semi-frenemies.

“As soon as we got to Australia (for filming), you look at this environment and it can be just breathtakingly beautiful and it can also just be incredibly frightening,” Theron says. “You're dealing with two human beings. One might have started the chase, but now two are kind of stuck, and the only way that they're going to survive is by helping each other.”

Theron didn’t come in with a bunch of extreme-sports skills. “I could run. So that came in handy,” she says with a laugh. She found a rock climbing gym in LA, and pro climber Beth Rodden came down from Yosemite to train her for a couple of months. “There's a big psychological component to climbing,” Theron says, “and I think the physical combined with that to me was very much representative of this movie.”

She also thought she’d take to kayaking quickly. Not so much. “I love water. Water is a second skin to me. I'm not scared of water. I feel very natural in water. And that turned out to be my biggest challenge,” Theron acknowledges. “Kayaking to that level is not easy and I really struggled with it.”

Theron had to have two surgeries on her elbow for an injury sustained during filming, and she couldn’t do any rock climbing for six months, but she’s back in the climbing gym now. And Rodden invited her up to Yosemite.

“It’s an opportunity that I just cannot pass on,” she says.” So I'm really trying to hit the gym as much as possible, but it's just really great to be back on the wall.”

As for the kayaking? “I will not be buying a kayak anytime soon.”