I don't like presumption of what another person must believe in matters of religion.
I didn't answer the question in the poll because it wasn't pertinent to my post but my answer is I have no way of knowing. I wasn't there and neither was anybody else among those who wrote down the words in the Bible. So all we have is our faith as to what we believe the Bible is telling/teaching us. I personally believe the story of Noah and the flood is most likely allegorical teaching but I never argue with those who take it literally because in the grand scheme of things I don't think it matters.
I do believe the story came out of oral traditions which is how stories got passed down from generation to generation in those days. And almost every single culture of that time in that area has a flood story. This suggests that at some point there was a massive flood. And with people who had never traveled, had no science education of any kind, it probably appeared to cover the entire earth. And that's how it made it into the lore/traditions of the ancient people who over the generations would become modern day Jews.