The Flood cannot have been local, else there would have been absolutely no need for an Ark or collection of animals. Noah had 40 days to shift to another region of the world. If he could build a titanic boat in 40 days, he could have just built a small one and moved onto India or somewhere.
The mathematicians knocked on the door and took the biologists' single ticket, before hurrying off to the other toilet to pull the same trick they did last time. :D
The Jains described microorganisms in the 23rd century BCE. A Roman scholar described germ theory in the 1st century AD. Does that make Jainism or Roman mythology the correct religion?
If the Flood were not planet-wide, this would remove the need for Noah to:
a) Build an Ark
b) Collect up the animals
Both could have been easily solved by just moving beyond the watershed of the soon-to-be-flooded area.
Do you therefore also postulate that the Jains in 2,300 BCE and Varro in the 1st century also had microsopes? The point I make is that it is perfectly possible to guess things correctly without actual direct observation. The thing is, millions of ancient peoples were speculating on the natural...