Genesis 6:2 Sons of God. Possibly fallen Angels, which God punished and are in chains until the judgment.
Genesis 6:3 The Holy Spirit played a most active role in the OT. The Spirit had been striving to call men to repentance and righteousness, especially as Scripture notes, through the preaching of Enoch and Noah. God declares that man has 120 years to repent before he destroys the earth with a flood.
Genesis 6:4 Either the offspring of the Sons of God and the daughters of men, who because their fathers were fallen Angels, they had superhuman qualities, or they were in existence at the same time as the offspring of the Sons of God and daughters of men.
Genesis 6:7 Regretted is sometimes translated grieved. God destroys everything excluding what lives in the water.
Genesis 6:9 God mentions Noah for he will preserve the continuation of the Godly line.
Notes: Only Noah at this time walked with God.
Genesis 6:11 Corrupt…filled with violence - The seed of Satan, the fallen rejectors of God, deceitful and destructive, had dominated the world.
Genesis 6:14 God declares to Noah that he will preserve him and his family, plus two (male and female) of every flesh on the earth, plus food provisions in the safety of boat that will ride out God’s wrath upon the earth. After the flood, those in the flood will start fresh all over again.
Genesis 6:15 The Ark - A cubit was about 18 inches long. In modern measurements, the ark would have been around 450 feet long, 75 feet wide, and 45 feet high, yielding a displacement of about 43,000 tons. A gigantic box of that size would be very stable in the water, impossible to capsize.
Genesis 6:18 Covenant - In contrast with the rest of the created order that God was to destroy, Noah and his family were not only to be preserved, but they were to enjoy the provision and protection of a covenant relationship with God. This is the first mention of "covenant" in scripture.
For if God did not spare angels when they sinned, but cast them into hell and committed them to chains of gloomy darkness to be kept until the judgment; if he did not spare the ancient world, but preserved Noah, a herald of righteousness, with seven others, when he brought a flood upon the world of the ungodly;
And the angels who did not stay within their own position of authority, but left their proper dwelling, he has kept in eternal chains under gloomy darkness until the judgment of the great day—
(Jude 1:6 ESV)