It seems she can thank her kids for persuading her to take the part in the upcoming DC blockbuster.
“My daughters were like, ‘Do you get to wear a crown? Do you get to have a tail?’” she recalled.
“I said, ‘I get to have mother of pearl all over my body,’ and they were like, ‘Oh do it mummy!’ and I wanted to have some fun.”
She’ll be joining an all-star cast: Jason Momoa plays Aquaman, Amber Heard is Mera and Patrick Wilson as Orm.
Kidman had previously also said that the promise of working with director James Wan was a very tempting prospect.
“The reason why I love [Aquaman] is James Wan is an Australian, and I’ve followed his career since he started,” she beamed.
“He’s a really good friend of mine, and he offered to let me play Queen Atlanna.
“As soon as he said I could wear mother-of-pearl and be a mermaid warrior, I said, ‘I’m done! Please! If there is one thing I have to do in my life, I have to be that!’
“Because you’ve got to have some fun.”
Aquaman will follow Justice League, which releases at the end of this year.
That itself will come hot on the heels of Wonder Woman, which has had incredibly positive buzz after early screenings.
Aquaman is out on December 21, 2018.