Contradiction with Genesis 7:21-23
These verses describe the destruction of all life on earth, yet Genesis 8:18 describes Noah and his family, along with some animals, leaving the ark, suggesting they survived the flood.
Genesis 7:21-23: And all flesh died that moved upon the earth, both of fowl, and of cattle, and of beast, and of every creeping thing that creepeth upon the earth, and every man:
Contradiction with Genesis 6:13
This verse states that God decided to destroy all flesh because of the violence on earth, but Genesis 8:18 implies that some creatures survived since Noah and the animals left the ark.
Genesis 6:13: And God said unto Noah, The end of all flesh is come before me; for the earth is filled with violence through them; and, behold, I will destroy them with the earth. [with the earth: or, from the earth]
Contradiction with Genesis 9:11
God promises not to destroy all life with a flood again, implying the previous flood was meant to eliminate all life; however, Genesis 8:18 shows that Noah and the animals survived.
Genesis 9:11: And I will establish my covenant with you; neither shall all flesh be cut off any more by the waters of a flood; neither shall there any more be a flood to destroy the earth.