According the the scripture, Genesis 6: 1 – 22. Human beings had spread over the earth, and daughters are born. Some of the heavenly beings saw the daughter of men were beautiful, and they took the one they like.
They had intercourse with them as a result; some gave birth to giants and strong men.
The whole earth has now gotten corrupted that God was sorry to have created people. He was filled with regret and said he would wipe the entire human, including the animal and birds.
There was a man called Noah; he had three sons, Shem, Ham, Japheth. Noah was the only man God seen righteous. God was pleased with him because he fellowshipped with God.
One day God called Noah, he said to him, I want to destroy the human. I want to send a flood to kill all living things on earth and make a covenant with you.
God commanded Noah to build an arch, making it 450 feet long, 75 feet wide, and 45 feet tall, leaving a space 18inches between the roof and the sides. Build it with three decks and a door in the side.
Go in to the ark with your wife, your sons, and their wives. Take into the boat male and female of every kind of bird and animal to keep them in existence. Take all types of food for you and them. Noah obeyed God and did what he commanded him.