The flood narrative: God saw that Noah was righteous in that generation, meaning that Noah was honest about dependence on God, in contrast to the rest of the human population generated according to the flesh, dominated by the corruption of Adam. Seven pairs of clean animals were on the ark since they would be used for sacrifice later on. Noah was 500 years old at the end of chapter 5, and in this passage, he is 600 years old. One hundred years is long enough for Noah and his sons to build the ark by hand and a very long time for people to consider its significance.
The fountains of the great deep were broken up and the windows of heaven were opened; the waters below and above (Gn 1:6ff) were brought upon the earth and covered even the highest point(s) by twenty two and a half feet. There were forty days and night of rain because “40” has to do with creation (4) and the law the governs (10). Forty will be a recurring number throughout the Bible, e.g., Israel’s wandering in the wilderness and Jesus’ time of temptation (see podcast on Matthew 4).