I love it when people say "oh the flood could never have happened because everyone knows that Miracles are impossible."
A world wide global flood as described in the Bible never happenned - at least not while man has been on the planet. If it had happenned that recently in geological history there would be irrefutable evidence and far fewer species of fauna and flora.
That's not to say miracles don't happen just thata world-wide flood didn't.