The Barney's Version actress was asked by Metro about previous reports that she is a fan of skinny dipping.
Pike said: "I'm a fan of water in general. I can't go past a lake or a piece of water without getting into it.
"I'm not a nudist or an exhibitionist but if I haven't got a bikini, I'll go in without a bikini."
She added: "There are some beautiful places in the Lake District. I've been swimming in western Scotland, which was freezing.
"There was a lake when we were filming Pride & Prejudice. I don't even know if I was allowed to go in it. I probably wasn't."
> Click here to watch our recent interview with Rosamund Pike