What's the difference between thinking there was an ark and there wasn't one? Do you have evidence either way? There WAS a large flood in the area due to a large natural dam break around what is now the Strait of Gibraltar, and nearly every culture in that area of the world has an ancient tale of a "flood" and how "someone saved a great deal by building a large boat." While I don't think anyone seriously believes that every animal in the world was taken 2 by 2 onto the ark, it is reasonable to say that there may have been a farm village that saved all of it's animals in this method- hence the story. Time and exaggeration probably made the legend to what it is today.
People with that spiteful "IF IT'S IN THE BIBLE IT'S HOGWASH" attitudes are just as annoying as the literal translation bible thumpers. There's a lot of history in the bible, and it can be used as a tool to uncover our past.