A rising and overflowing of water to cover the land, specifically the flood associated with Noah in Genesis 6–9.
Biblical Account
The story of Noah’s flood is told in Genesis 6–9. It is mentioned often in the Bible, always as a real event (Genesis 10:1, 32; 11:10; Matthew 24:38–39; Luke 17:27; 2 Peter 2:5). In the Bible, God sent the flood because of sin, which was so bad that “the wickedness of man was great upon the earth” (Genesis 6:5). God decided to destroy everyone and start again with people who would obey him (compare Genesis 1:26–28). The only people who were faithful to the Lord were Noah, his sons, and their wives. God used them to recreate the earth after its destruction.
Noah spent 120 years building a great ship and warning people about God’s coming judgment (Genesis 6:3; compare Hebrews 11:7; 1 Peter 3:20; 2 Peter 2:5). When the flood came, it rained heavily, and the underground waters rose (Genesis 7:11). Only Noah's family and any land animals he brought onto the ship were saved from the water. The flood lasted for more than a year. Finally, the waters went down, and the earth was dry again (Genesis 7:6–12, 24; 8:3–6, 10–14). When Noah and his family left the ark, they gave sacrifices to God to thank him. God promised he would never send another flood to destroy the earth.
The Size of the Flood
Those who believe the flood account is true disagree about its size. The story seems to suggest that the whole earth was flooded as high as the top of the highest mountains (Genesis 7:17–20; 8:4). Some have argued that waters that were high enough to cover “all the high mountains under all the heavens” (Genesis 7:19) would cover the entire earth. Those who argue for a local flood note that the text says that it appeared that all the earth was flooded. So, a worldwide flood was unnecessary. God wanted to destroy humans, who may have only lived in Mesopotamia at that time. Others argue that in the Bible, “earth” is often not meant literally. In Genesis 1:1, “heaven and earth” means "the universe." Sometimes “earth” describes a single country (Genesis 47:13), the soil itself (23:15), and so on. So, it isn't necessary to think that the Genesis flood story implies the entire world was flooded.
Some people who believe in a universal flood argue that there are marine fossils on the tops of mountains, so the water must have covered them. Others disagree, saying that all mountains originally came from the seas, so it is reasonable that there is evidence of marine life on them. Theological beliefs and interpretations of the Bible determine whether people think the flood was global or local. See “Scientific Evidence for the Flood?”.