The 23-year-old musician, who is making his feature film debut with the Christopher Nolan-directed film, said he was so exhausted due to the strenuous shooting schedule that he ended up nodding off with the camera on, reported People magazine.
"Boats, sides of boats, swimming... I definitely fell asleep while floating a couple times. It was nice, good, refreshing.
"I slept most of... I'd say 90 per cent of what wasn't filming, I was asleep," Styles said.
The "Sign Of The Times" singer plays a young soldier, Alex, stranded on the beach at Dunkirk with other warriors from the Allied forces.
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