Most interpretations of the Biblical story of Noah and the Flood assume that the story is either entirely literal or entirely figurative (and therefore fictional). This assumption is unwarranted. Many Scripture passages contain both literal and figurative elements. For example, Jesus tells the disciples that Lazarus is sleeping — He is using a figure. Then He explains that Lazarus is dead — now He is speaking literally. Even the expression Love your neighbor contains both literal and figurative elements. The term love is literal. The term neighbor is a figure, meaning that we should treat even persons who are not our neighbors as if they were.
So we can hold that there was literally a Noah and a great Flood and an Ark with animals. But we can also hold that the story includes certain figurative elements: that the Flood covered all the earth, that the Ark contained all animals, that all humans were killed other than in the Ark, etc.
Any argument that proves the Flood could not have covered the whole earth, or that all human persons could not have been killed at that time, or that all animals could not have fit on the Ark, only proves that those elements are figurative. It does prove that the entire story is fiction.
As for the timing of the Flood in human history, if it is a figure that all human persons were killed, and all animals were killed, by the Flood except those on the Ark, the date of the Flood can be place much more recently. We do not need to place the Flood so long ago that the entire human race and all animal species could repopulate the entire earth.
W. Bruce Masse has a theory on the dating of the Flood, a theory which I think is correct. After examining many ancient Flood myths, and their similarities, he concluded that these myths could not be so similar by coincidence; there must have been an actual event upon which these stories are all based.
That point is interesting, but this next point is amazing.
He found some cultures that described a comet in the sky prior to the Flood, and which also described the appearance of the stars and planets in the sky at that time. The description of the sky allowed him to date this comet sighting to the spring of 2807 B.C. And he further theorized that a comet striking the Indian Ocean caused the great Flood at that time.
How can a comet cause a Flood?
The comet would strike the ocean with incredible speed and force, reaching all the way to the sea floor, creating immense mega-tidal waves, and throwing immense amounts of water into the upper atmosphere. The result is a subsequent worldwide rainfall lasting many days. The mega-tidal waves have such a strong and lasting effect on the shores in every direction, that Masse was able to see those effect (from satellite imagery) even today, and to trace the direction back to the location in the Indian Ocean.
Scripture says that the waters of the Flood came from below and from above: “all the fountains of the great abyss were released, and the floodgates of heaven were opened.” (Gen 7:11). The great abyss here refers to the depths of the ocean, and the floodgates of the heavens is rain from the sky.
A comet strike that throws water into the upper atmosphere would take water from the great abyss and cause the figurative floodgates of the heavens to be opened.