Then his disciples were liars and Jesus was an idiot for picking them.
You can't have Jesus as Lord and not believe that Noah's flood was an actual event. Jesus didn't leave you that option.
Either he was a fraud or he was the Truth. Take your pick.
"Then his disciples were liars and Jesus was an idiot for picking them."
Or they were misquoted.
But since the evidence is overwhelming that there was never a universal flood and the human race is not descended from eight survivors who lived only a few thousand years ago, one can easily conclude that Scripture is inaccurate. Whether that leads one to conclude Jesus didn't actually utter those words (and the author simply made it up), or that Jesus lied, or even that Jesus didn't exist, it appears to be a personal matter.