It says that in less than 1700 years God went from "Let us make man in our image" to "I will destroy man whom I have created from the face of the earth; both man, and beast, and the creeping thing, and the fowls of the air; for it repenteth me that I have made them."
It says that a 600 year old man built a 32,000 sq ft, 4 story high wooden boat
In Gen 6:19-20, it says that Noah should bring 2 of every animal on the ark, but only 4 verses later in Gen 7:2, it says that Noah should bring 7 pairs of all the clean animals and 2 of all the unclean animals
It says that, for a second time, all of mankind is the product of incest amongst one family
It says that all land animals were killed except those on the ark which came to rest on Mount Ararat; yet somehow land animals came to exist on islands and continents that those animals could not reach on their own.
It says that, according to the Usher dating, this all happened just 4362 years ago, even though there is no evidence of a worldwide flood and there is evidence of contemporaneous civilizations that were unaffected.
But thankfully, it also says that god creates rainbows so he will remember not to kill us all again...
-- From Genesis 6:5 - Genesis 9:19: (though people should definitely read the verses right before and right after for even more weirdness...)