Harry Styles had a gruelling experience shooting for 'Dunkirk'

Singer-actor Harry Styles says filming his debut movie "Dunkirk" was a "gruelling experience" for him.

The 23-year-old musician says he had a trying time while shooting a water sequence fully-clad in clothes for the film based on World War II, reported FemaleFirst.

"A week before we started, Emma (Thomas, the film's producer) called me and said, 'By the way, I forgot to ask... you can swim right?'

"It was a relief to know that I could because there was so much swimming involved. However much you train for it, filming in the water for an hour in full clothes is a gruelling experience," Styles says.
 

The "Sign Of The Times" singer adds the director of the film, Christopher Nolan is a ball of energy and "leads by example".