Genesis 7:17-24 New International Version (NIV)

17 For forty days the flood kept coming on the earth, and as the waters increased they lifted the ark high above the earth. 18 The waters rose and increased greatly on the earth, and the ark floated on the surface of the water. 19 They rose greatly on the earth, and all the high mountains under the entire heavens were covered.20 The waters rose and covered the mountains to a depth of more than fifteen cubits. 21 Every living thing that moved on land perished—birds, livestock, wild animals, all the creatures that swarm over the earth, and all mankind. 22 Everything on dry land that had the breath of life in its nostrils died. 23 Every living thing on the face of the earth was wiped out; people and animals and the creatures that move along the ground and the birds were wiped from the earth. Only Noah was left, and those with him in the ark.

24 The waters flooded the earth for a hundred and fifty days.

Was the flood so big it covered the entire earth? This is certainly possible. There is enough water in our oceans to cover all the dry land on earth. The earth did begin this way as it tells us in Genesis 1:9-10, 

Genesis 1:9-10 New International Version (NIV)

And God said, “Let the water under the sky be gathered to one place, and let dry ground appear.” And it was so. 10 God called the dry ground “land,” and the gathered waters he called “seas.” And God saw that it was good.

God promised never to flood the earth again. This flood had destroyed all the inhabitants of the earth. The flood was sent to destroy all the world’s wickedness. It would have taken a flood to cover the earth to do this. At the end of the flood, Noah’s boat touched down in the mountains of Ararat, located in Turkey. It took 8 months before Noah and his family could step onto dry land.