We often read the story of the flood and see God's judgment of a sinful world as a "mean" or destructive thing. But we need to look at this story from the perspective of Noah and his family - they were saved because God "covered and washed away" their sin. When man fell into sin, they were cursed and so was the ground. There is much debate as to whether the flood covered the whole earth or just the "known world" at the time of the flood. No time to debate that here. The point the bible is trying to make is that God covers all our sin, He covers it completely. God washes away all sin and if we have faith in God and are obedient to Him like Noah was, we also will be washed, covered, and saved.