Genesis 6:4

6:4 The Nephilim were on the earth in those days (and also after this) when the sons of God were having sexual relations with the daughters of humankind, who gave birth to their children. They were the mighty heroes of old, the famous men.

Genesis 7:23

7:23 So the Lord destroyed every living thing that was on the surface of the ground, including people, animals, creatures that creep along the ground, and birds of the sky. They were wiped off the earth. Only Noah and those who were with him in the ark survived.