Those who have not yet relinquished their right to think for themselves should be virtually certain that the story of Noah and the Ark is a fable. Those who believe the Bible's stories are literally true find it almost impossible to address with a straight face the problems presented below.
Then the flood came which destroyed every living thing which was not in the Ark: "And every living substance was destroyed which was upon the face of the ground, both man, and cattle, and the creeping things, and the fowl of the heaven; and they were destroyed from the earth: and Noah only remained alive, and they that were with him in the ark." (Genesis 7:23)
Now, it is hard enough to understand why the disappointed Lord could not have just waved his hand to make the necessary improvements in existing man instead of killing every human being on earth, but nearly incomprehensible is the Lord's decision to drown the whole planet, destroying "every living substance." After all, the Lord spent the entire third day of creation making the grasses, herbs, and fruit bearing trees (Genesis 1:11-13), and the fifth day making animals (Genesis 1:20-23); why would his anger at man lead him throw all this other good work down the drain? Couldn't the omniscient God think of a way to kill man without killing the grass and animals, too? The grass hadn't offended God, and the animals hadn't done anything wrong, had they? God gave Noah seven days to get ready. How did Noah and his sons build such a huge ark in just seven days? How did Noah cause the animals to come to the Ark? How did they know where it was, and when they had to be there? How did the great white bears and penguins of the polar regions, the kangeroos of the southern hemisphere, and the snakes and gorillas of the tropical rain forests cross the vast oceans and land masses to the Mideast? Once the whales, porpoises, and dolphins got to the Ark, how did they travel up the gangplank? Did the slow-moving snails and turtles from other continents head for the Ark at the same time as the other animals? Did weather conditions permit travel in all cases? How did the polar bears and penguins survive the heat of the Mideast? How were the lions prevented from eating the lambs? The vegetation which many animals eat grows only in their natural habitat; did they bring it with them, and how was it kept fresh for 150 days? How did just eight people manage to feed millions of species? How did Noah and his small family keep track of the special diet of each of the millions of species of animals, and remember which had already been fed, and when? Assuming only two million species of animals, each person on board the Ark would have had to supervise the care and feeding of 250,000 different species each day, some of which would have required three or more feedings per day.
Joseph F. Alward
"Skeptical Views of Christianity and the Bible"
http://members.aol.com/jalw/joseph_alward.html