Although Jason Momoa’s Arthur Curry is the titular hero and the one on the posters, he’s not the only badass underwater warrior in Aquaman. Amber Heard’s Mera is a fierce fighter in her own right, with the swimming skills to make Michael Phelps look like a slow-moving seahorse. And although she probably can’t talk to fish, Amber Heard still felt like a superhero filming Aquaman, as she explained:

Jason Momoa may be the one with his shirt off, but clearly Amber Heard had to do a lot of training for the film as well. To get ready for the Aquaman‘s fight scenes, she and Jason Momoa both had to undergo a regular schedule of grueling training in martial arts like judo and jiu-jitsu, as well as the actual fight choreography to look convincingly skilled onscreen.

All that training undoubtedly got Amber Heard in great fighting shape and she likely picked up a few things skill-wise as well. That, and getting to actually use those skills and choreography to be a warrior in the film itself, had the actress feeling superhuman, just like the superhero she plays.

As Amber Heard told ET, she felt superhuman after all that training, and that’s just testament to the power and benefit of exercise and martial arts instruction. All that exhaustion makes you into a better version of yourself, a superheroic you that feels more capable, like you could punch through walls and just maybe, ride a shark into battle.

Being a warrior with a sword and crown is a big part of why Amber Heard joined the DCEU as Mera in the first place, so it must be especially rewarding to actually feel like a superhero while shooting Aquaman.

That Amber Heard felt like a superhero filming Aquaman will hopefully come through when we see her character in the film. Mera already proved her fearlessness and combative skills in Justice League when she took the fight to Steppenwolf, and Aquaman will give her even more time to shine and fight by Arthur’s side.

Aquaman is finally in the can and ready for its December release date. The early tracking on the only DCEU film this year had it pegged in the $ 40 million to $ 60 million range opening weekend, but there is still plenty of time for that to shift as the film’s marketing ramps up closer to release.

Aquaman is especially anticipated among women according to one poll. Many of those female audiences may be eager to see Amber Heard’s Mera, as well as Nicole Kidman’s Queen Atlanna. Or maybe it’s the Jason Momoa factor; probably a little column A, little column B.

James Wan’s Aquaman splashes into theaters on December 21. Check out our Holiday Movie Guide for Aquaman and all of the blockbusters and awards contenders coming to theaters this holiday season.