Amber Heard wearing a swimming cap to 'Aquaman' premiere. (Picture: Instagram)

The 32-year-old actress - who plays future Queen of Atlantis, Mera, the love interest of the titular Aquaman in science fiction flick -stepped onto the red carpet on Monday night (26.11.18) at London's Cineworld in Leicester Square, wearing a Valentino haute couture green outfit with a matching swimming hat. 

Amber Heard wearing a Valentino haute couture swimming cap. (Picture: Instagram)

The 'Justice League' actress wowed fans in an emerald look from the autumn/winter '19/'19 collection of Pierpaolo Piccioli - the man responsible for Ezra Miller's extravagant red carpet looks - paired with gold Brian Atwood platform heels. 

The stunning gown was emblazoned with green-and-gold-foil floral detailing and boasted a plunging neckline and trailing skirt with a thigh-high slit which the star paired with a simple gold bangle and a long neck chain. 

Amber wore a Valentino haute couture green outfit with a matching swimming hat. (Picture: Instagram)

Although the blonde beauty channelled her fantasy alter ego for the red carpet, she admitted she constantly felt "uncomfortable" being submerged in water for the shoots and felt like she was "being hugged by baby angels" when she was allowed to wear a coat during breaks.

She previously said: "It was, how uncomfortable can I be? When I got to put a coat on for a few scenes out of the water, I felt like I was being hugged all over my body by baby angels. I didn't want to go back to my Atlantean suit."

The star also recently revealed she had to work out for five hours day to get in shape for the film.

She said: "I did six months of rigorous training. It was a lot of weight and strength training, as well as special martial arts training. By the end, I was working out for five hours a day."