Before the Great Flood the Bible tells us that mankind's behavior degenerated to where people's minds were thinking about "only evil continually" and "the earth was filled with violence." Our righteous God became sorrowful for having created people who became so wicked. So, God decided to destroy all people, all land animals, and all birds. (Gen.6:5-7, 11).
Noah was trying to live righteously in this wicked world, so God was merciful to him and his family. (Gen. 6:8-9; 7:1). Noah was given instructions about how he was to build a big boat--450 feet long, 75 feet wide, and 45 feet high. (Gen. 6:14-16). I am told that its dimensions were similar to today's oil tankers, making it practically impossible to overturn even in the worst storm at sea.
God told Noah, "Everything that is on the earth shall die" by a flood. (Gen. 6:17; 7:4). Noah was also told that the Ark would save his family (four married couples) and a male and female pair of every kind of"unclean" animal and 7 each (or 7 pairs) of every "clean" animal. (Gen.6:18-19). Noah was also instructed to store food in the Ark for hisfamily and for all the animals. (Gen. 6:21).
Noah did "all that God commanded him." (Gen. 6:22; 7:5).
Seven days before the rain started, God ordered Noah, who was 600 yearsold, to come into the Ark with his family and all the animals. (Gen.7:1-4, 6). God sealed them in the Ark. (Gen. 7:16). God caused water toboth rise up from below the earth and to fall from the sky for 40 days, until the water was 22 feet deep over the highest mountain. (Gen.7:11-12, 19-20). Everyone and everything that had lived on dry ground was drowned. Only those in the Ark survived. (Gen. 7:21-23).
After 150 days the water began to subside. The Ark came to rest on a high mountain of Ararat. Three months later the tops of the mountains could be seen. (Gen. 8:3-5). When the surface of the ground was dry enough, the Bible says that God told Noah to go out of the Ark, 365 days after he entered it. (Gen. 8:16).
Later, God made a promise that "never again shall there be a flood to destroy the earth." The rainbow is the sign of His covenant. (Gen.9:8-17).