"That would be silly," Stewart, 29, told ET's Ash Crossan at the Underwater junket in Los Angeles on Tuesday, when told that she would have been great for the part. She also expressed how excited she was for her ex-boyfriend.
"No not at all. I mean, obviously that would [have been cool]. I've been watching Batman since I was a little kid, every iteration of that series," she continued. "That would've been a blast, but also I am, like, really good friends with Zoe. And obviously, I am so proud of Rob doing this whole [project]."
"I can't wait to see this movie. So, like, sure, that is a funny idea but the real version is going to be sick," Stewart said. Ever since starring in the Twilight franchise with Pattinson, and their high-profile romance and subsequent fallout, fans have been wanting the two to reunite.
For now, Stewart is putting all her efforts in her new thriller, Underwater. The movie is about mysterious creatures who terrorize crew members aboard a research station located seven miles below the surface of the ocean. For Stewart, who plays Norah, the experience being on set was a bit traumatizing.
"I found that any day we had to go down into the submersible suits, was really truly harrowing," Stewart revealed. "I'm really claustrophobic so some of the other actors really enjoyed going underwater, I did not. I think I took Xanax and cried on the days I had to actually go under the water…Not to sound dramatic, I know it's hard to hear actors complain how hard movies are to make, but this one genuinely, actually was like, I think a primary plot of the movie is us getting through making this movie."
Fear aside, Stewart loves making action movies. "They are just not fun to make. Theoretically, they are fun, you overcome fears and put yourself in the moment physically and really test yourself," she explained. "But they hurt, they are super scary, they take forever, underwater everyone."
She also shaved her head for the role, explaining that it was difficult to get out of the suit and that in the beginning of the movie, her character is "someone who is not quite tender with herself." "She isn't very nice to herself in the beginning of the movie," adding that she is a "sad person who is, 'Yeah, I don't need to be pretty, I don't need to have anything holding me down.' Slash, I just really wanted to shave my head and this gave me a good excuse."