Genesis 7:16-20

Those which entered, male and female of all flesh (creatures), entered as God had commanded Noah; and the LORD closed the door behind him. The flood [the great downpour of rain] was forty days and nights on the earth; and the waters increased and lifted up the ark, and it floated [high] above the land. The waters became mighty and increased greatly on the earth, and the ark floated on the surface of the waters. The waters prevailed so greatly and were so mighty and overwhelming on the earth, so that all the high mountains everywhere under the heavens were covered. [In fact] the waters became fifteen cubits higher [than the highest ground], and the mountains were covered.