Jodie Foster experienced her "worst nightmare" while a scene for 'True Detective: Night Country'.

Jodie Foster experienced her "worst nightmare" while filming a particularly tough scene for 'True Detective: Night Country'.

The 61-year-old actress played the tough cop Chief Liz Danvers in the latest installment of the limited series and she admitted a scene where she had to fall through the ice was terrifying because the water tank was pitch black and she her clothes had deliberately been weighted down.

Asked which scene she had expected filming to be "hell", she told Robert Downey Jr. for Variety's Actors on Actors series: "Falling through the ice. Because I kept saying, 'How are we going to do it?' And they'd be like, 'Oh, we'll see.' Because it's at the end. But we're not really falling through the ice, right?

"Yeah. So we shot that on a big tank. And it's entirely dark, maybe 150 feet down.

"I work with a free diver, who's like, 'This is how we hold our breath in a way that allows us to keep going down. I'm going to be off to the side. When they say 'Cut,' I can swim to you and save you.'

"They weighted every jacket so I couldn't get to the surface, and I had big boots on.

"The thing I hadn't anticipated was that I couldn't see anything in front of me. It was actually my worst nightmare.

"Usually, it's the opposite when you designate something like, 'This is going to be bad.' But when I got there, it was bad."

But despite the tough scene and the extreme temperatures, the Oscar-winning star loved shooting in Iceland.

She explained: "There's live music everywhere. The food is delicious. They have geothermal baths everywhere. Instead of going to a pub, you go to the baths.

"But 58 nights outside in subzero temperatures is tough. You have the clothes on and the little hot pads. I had hot pads in my hat. However, you still have to breathe.

"So you have to do exercises where you breathe into your hands to get your lungs ready for the fact that you're going to hit this cold winter.

"When you take on a limited series, you immerse yourself in the culture. And if you do it right, that informs everything you're doing."