Actress Evan Rachel Wood was pranked by her Ides of March co-star George Clooney at the Venice Film Festival in Italy when he persuaded her to go for a late night swim fully clothed by insisting he'd join her in the pool.

The gullible star was still on a high after serenading Clooney and her castmates in a karaoke bar and thought nothing of diving into the hotel pool when Clooney told her it was traditional for the cast to go for a late-night dip.

She says, "After I sang, I was kinda on this high, this adrenaline rush... so I jumped in the pool in my gown and no one followed me... He (Clooney) said the whole cast was gonna do it.

"I ended up in there alone, but I just went, 'Oh, whatever', and I was, like, having this amazing cathartic moment, floating in this pool in this gown, and then this security guard's head just came into frame and the moment was ruined and I got in trouble and I got kicked out.

"I had to return that dress to the designer and I don't think they knew, until probably right now, that that happened."