Actress Emma Watson fell sick on the set of biblical epic Noah after drinking a mug of stagnant water.

Director Darren Aronofsky banned plastic water bottles on set to keep the production environmentally-friendly, but after hours of filming in the early hours of the morning, Watson was desperate for a drink and accidentally sipped from a cup which had been sitting in her trailer for three months.

Watson tells Wonderland magazine, "Everything we used had to be recycled or recyclable. Having no water bottles on set at five in the morning, when you're exhausted and delirious, wasn't ideal.

"I was so tired one morning I picked up a mug from my trailer and drank some stagnant water that had been there for the duration - so three months. I was so ill."

Rather than give the Harry Potter star a day off sick, Aronofsky insisted she used her illness in the film.

She adds, "I came in the next day and was like: 'Darren, I don't think I can do this, I'm really sick'. He was like: 'Use it for the scene.' And I... was like: 'Is he joking? He is joking right?' and there was deadly silence."