We asked Stewart about taking the plunge.

How would you describe the movie?Its a really dark, scary meditation on isolation.

Theres this fragile nature that this girl has, and you just never really know why.

UnderwaterKristen Stewart and Vincent Cassel

Credit: Alan Markfield/Fox

Information about her sort of filters out throughout the really traumatic events.

You wrapped production over two years ago.

How are you feeling now that its finally hitting theaters?Im stoked.

UnderwaterVincent Cassel, Jessica Henwick, TJ Miller, Kristen Stewart

Alan Markfield/Fox

I havent made a movie of this scale maybe ever.

It was not an easy movie to make really long and just drippy and cold and fing hard.

I want to see how we all reacted in such precarious circumstances.

UnderwaterKristen Stewart

Alan Markfield/Fox

It really pulls out the best and worst parts of people.

What were some of the biggest challenges of filming?The suits were really heavy, honestly.

We couldnt move around.

I really dont like being held down, I dont like confined spaces, Im not a strong swimmer.

Thats kind of what it felt like to make the movie as well.

Like we were all dying!

Underwaterhits theaters Jan. 10.

(The issue will beavailable on all newsstands starting August 22.)