Well, the account of the Flood includes these words:
“19 And the waters prevailed exceedingly on the earth, and all the high hills under the whole heaven were covered. 20 The waters prevailed fifteen cubits upward, and the mountains were covered.” (Ge 7:19-20 NKJV)
How could it not cover the whole earth if all the high hills under the whole heaven and the mountains were covered? And what was the point of the ark, if there was dry land that Noah and his family could have escaped to? Then we are told the effects of the Flood:
“21 ¶ And all flesh died that moved on the earth: birds and cattle and beasts and every creeping thing that creeps on the earth, and every man. 22 All in whose nostrils [was] the breath of the spirit of life, all that [was] on the dry [land], died. 23 So He destroyed all living things which were on the face of the ground: both man and cattle, creeping thing and bird of the air. They were destroyed from the earth. Only Noah and those who [were] with him in the ark remained [alive].” (Ge 7:21-23 NKJV)
None of that would be true if there were people and animals still living in some supposed non-flooded areas.
Where does Genesis 1 "say they aren't literal 24 hour days"? It says over and over that each of the days had a morning and an evening.
The narrative includes hyperbolic language, and it is written in part, as polemic against the Mesopotamians flood epic with the apkallu, or the 7 sages.
It is similar to saying "my suitcase weights a ton!!!". And then 2,500 years later, someone comes around and asks "well how could the suitcase not weight over 2,000 points if it says "my suitcase weights a ton???" ".
For example, read closely here:
Genesis 8:3-9 ESV
[3] and the waters receded from the earth continually. At the end of 150 days the waters had abated, [4] and in the seventh month, on the seventeenth day of the month, the ark came to rest on the mountains of Ararat. [5] And the waters continued to abate until the tenth month; in the tenth month, on the first day of the month, the tops of the mountains were seen. [6] At the end of forty days Noah opened the window of the ark that he had made [7] and sent forth a raven. It went to and fro until the waters were dried up from the earth. [8] Then he sent forth a dove from him, to see if the waters had subsided from the face of the ground. [9] But the dove found no place to set her foot, and she returned to him to the ark, for the waters were still on the face of the whole earth. So he put out his hand and took her and brought her into the ark with him.
1. The waters receded from the earth.
2. The ark came to rest on the mountains of Ararat.
3. The tops of the mountains were seen.
4. It went to and fro until the waters were dried up from the earth.
Now think about these words above. Now read verse 9:
"But the dove found no place to set her foot, and she returned to him to the ark, for the
waters were still on the face of the whole earth."
Wait a minute, the dove found no place to set her foot? But what about the verses that describe waters receded and dried from the earth, and the tops of mountains being seen?
The text can't actually be read in a bluntly literal way, or this produces lots of odd contradictions, such as this one.
Here is some background context for the flood narrative to help explain:
I would also recommend "The Lost World of the Flood" by Dr. John Walton and Dr. Tremper Longman III in which they give several direct parallels between the flood narratives of the epic of Gilgamesh and of the Genesis flood.
And, in order to understand the Genesis 6, reading the book of Enoch or the book of the giants, is mandatory for context.