The flood survived by Noah's family and the animals they took onto the ark, was said to have wiped out all human and animal life on the Earth, to be started over by the inhabitants of that ark. Ironically, part of God's anger and reasoning for causing the flood were the Nephalim. In Genesis 6 we see that the race of Nephalim came along when the sons of god (El, not Yahweh) married the daughters of man and they bore children to them. It refers to them there as the "mighty men of old." In verse 5 God decides that this just isn't working out like he planned, so he starts preparing for Noah to build the ark so that he can try again.
So everybody's wiped out and mankind starts over with Noah and his family, right?
But wait! Centuries later (430 years, to be exact), after Israel has escaped Egypt and they're supposed to be getting ready to go into the land of promise, Moses sends 12 young men to have a look (Numbers 13). You are no doubt familiar with Joshua and Caleb, who end up leading Israel in the wilderness for 40 years while everyone else dies off. But who do the spies find in the land of Canaan that scare them so much? The Bible tells us that it's the Nephalim (verse 33). God went to all the trouble to flood the earth and wipe the people out, and the main ones he wanted to get rid of, these half-human half-god creatures, it turns out that their descendants are still around all these years later!
By this time, God Most High is gone and Jehovah his son is god of Israel, so he's stuck dealing with them. It'll be another 1500 years or so before Jesus, the son of Jehovah and the grandson of God Most High, comes on the scene. By that time, not only do the Nephalim seem to be gone, we see in Psalm 82 that Jehovah's brothers have lost their deity and have probably died.
The Bible is so much more interesting when you read what it actually says, instead of what they tell you in church. The Old Testament is a lot more interesting when you don't try to impose the New Testament on it. Seriously, this is almost as interesting as Norse mythology! Marvel needs to adapt these stories!