The 23-year-old British actress said she has always been "more spiritual, than specifically religious".
"I had a sense that I believed in a higher power, but that I was more of a Universalist," she told The Telegraph.
"I see that there are these unifying tenets between so many religions and I'm really interested in those things that are more far-reaching than culture, nationality, race or religion."
Despite her own ambiguity, Watson joined those who are looking forward to the debate Noah will stimulate, saying: "I think it's amazing to make a film that celebrates faith and that gets a conversation going, because it's such an important subject."
Although it doesn't open in the US until 28 March, Noah has already faced a significant amount of controversy. Many in the faith community have been particularly sceptical about the way in which the plot will retain biblical accuracy, while the film has been banned in several Muslim countries for its depiction of the titular character, who is also a prophet in the Koran.
Some Christians contend, however, that believers should welcome the opportunity to discuss their faith and use Noah as a springboard to share the Gospel.
Jonathan Snowden, biblical adviser for the film, believes it will be valuable in opening up reflections on the biblical narrative, mercy, faith and intimacy with God. "We can have fun, spirited debates of how you'd do it differently if you had $125 million to make your version of Noah's ark, but let's focus on the opportunity for now," he says in an article for the Christian Post.
Paramount Studios, which is keen to encourage a core Christian audience to support the movie, has responded to criticism by issuing a disclaimer to its marketing materials which states that the story remains "true to the essence, values and integrity" of Scripture, while taking some "artistic license".
Noah opens in cinemas across Australia on March 27.