There's a doubt I have about the story of Noah that I can't explain. If Noah's ark landed about 4000 years ago in what is now Turkey, how could some land animals get to places such as Australia or other islands? How can there be kangaroos in Australia, elephants in Sri Lanka, and bears in Japan? I know there must be an explanation, but this is really confusing and puzzling.
The entire survival and spread of people and animals after they left the ark was by a miracle. For example, there was not enough of any species in the ark to allow for a critical mass for the next generation to survive. Consider the passenger pigeon which became extinct when the flock size dropped below the millions within historical times. Thus, both the survival and the spread to the rest of the world was by a miracle. See also the posts on this site about the food required that was available only by a miracle. As soon as a meat eating animal would have eaten a pig, the entire species would have disappeared had they not first built up a full population miraculously.