The Nephilim were on the earth in those days-- and also afterward-- when the sons of God went in to the daughters of humans, who bore children to them. These were the heroes that were of old, warriors of renown.
The LORD saw that the wickedness of humankind was great in the earth, and that every inclination of the thoughts of their hearts was only evil continually.
So the LORD said, "I will blot out from the earth the human beings I have created-- people together with animals and creeping things and birds of the air, for I am sorry that I have made them."
And God said to Noah, "I have determined to make an end of all flesh, for the earth is filled with violence because of them; now I am going to destroy them along with the earth.
For my part, I am going to bring a flood of waters on the earth, to destroy from under heaven all flesh in which is the breath of life; everything that is on the earth shall die.
Of the birds according to their kinds, and of the animals according to their kinds, of every creeping thing of the ground according to its kind, two of every kind shall come in to you, to keep them alive.