So basically it all boils down to incest.

Look, I don't care if you religious types want to believe stories - regardless of how entirely full of holes and lacking in logic they are, or that basic empirical observation or the application of a modicum of rational, intelligent thought would quickly tell you maybe you should start questioning some things...

believe what you want. I won't try to stop you.

I'll just say this:

according to this story, there is 1 unrelated female, who gives birth to two daughters.
Now, for the human race to continue, I think you know full well what has to happen - considering the only males they could possibly mate with are direct relations - they would, in short, need to copulate with their uncles.

And then what?
The children these girls would have with their uncles would have who to mate with?
Oh yes, that's right. Family members again.

So you are talking about generations upon generations of incest-borne children.

Not to mention, sure didn't take long for all of those inbred kiddies to magically morph into the various groups you see today - Asians, Africans, Native Americans, Australian Aboriginals, etc. Nevermind that written language in China alone goes back further than the story takes place.

Also, don't you suppose there's one fairly MAJOR hole in this whole tale? Besides the ones I've already spoken of, I mean.

Yes, that's right. I'm talking about volume. The bible makes the dimensions of the ark quite clear. You're talking about a vessel less than 500 feet long and 80 feet wide. Smaller by far than the Titanic, for instance.
Now, do you realize just how many species - even ignoring those which can fly or swim - on this planet? Even if you only had two of each, you have to realize that there ARE:
Bird species number around 10,000 (known) - not all of which - in fact, a very significant portion of which - are incapable of flight or at the very least incapable of remaining airborne for as long as it would require for dry land to reappear. Furthermore, even assuming they could, what would they eat? Therefor, one must reason the vast majority of these 10,000 species would need to be aboard the ark. Birds are relatively small in most cases, but you are talking about 20,000 individual birds, which, small or large, are going to take up a massive amount of space even if you stacked them 40 feet high.
Next, you have the mammals. Of which there are roughly 5,400 species known to exist - and of those, the VAST majority are NOT aquatic - in fact nearly all mammal species with the exception of whales, dolphins, seals and sealions, are terrestrial.
Quite a lot of terrestrial mammals weigh in excess of 100 pounds and some weigh TONS. Even assuming an average weight of 20 pounds, you're talking about 216,000 pounds given two of each - 108 tons. But we all know well that there are also many large mammal species, so the total actually greatly exceeds that - THOUSANDS of tons.
Next, reptiles. Of which there are more than 10,000 of varying sizes between thousands of pounds and a few ounces. Add minimum another 20,000 animals.
Next....invertebrates.
Insects alone number about a million KNOWN species - vastly terrestrial. So perhaps two million insects on board.
Then of course you have other invertebrates, plant species which cannot survive underwater for extended periods of time There are millions of these.

Now, consider all of the above along with the fact that all of these animals are going to need FOOD (without eating each other), and you've got a serious problem. You would require enough bio-mass to outweigh the RMS Titanic, which was just under 900 feet long and 50,000 TONS. Far larger than the ark.

And, you also run into this issue: noah is shown allowing animals such as grizzly bears (north american, mind you), African elephants, Asian Elephants, kangaroos (Australian), Lions (African), and myriad other species on board which are only found in specific habitats and which are actually unable to survive in habitats outside of their norm - such as the polar bear. First of all, they would have had to swim across the oceans of earth just to reach Noah. Second of all, they'd have to survive in many cases in an environment they are not at all suited for and, by the way, EAT (problematic for the carnivores considering if they eat any of the other animals that species is kaput) - even some of the herbivores would only be able to eat certain types of plants found only in one part of the world which Noah would not have had access to. SO....how'd they survive?

Additionally, even if you assume the fish would be fine all by themselves by virtue of being able to swim - you'd also be wrong. A global flood would mix fresh and salt water, warm and cold, and this would actually prove QUITE disasterous for the fish of the world - saltwater species die quickly in fresh water and vice versa, with very few exceptions.

Finally, water volume - there simply isn't enough water present on EARTH - even if you melted all of the ice caps and dumped every drop of water from the atmosphere - to cover the planet with water - certainly not the mountainous regions. This includes the aquifers of earth -subsurface water just is not enough (we geologists have mapped that out quite well). In fact, it wouldn't even come CLOSE, if you actually bother to crunch the numbers.

Subsurface water alone would not even be enough to account for 1% of the volume needed to cover that much ground in 40 days and 40 nights.
Some rather bright people have calculated that in order for the rain to make up for the rest of it - in that time span - it would have to rain an average of six inches per MINUTE in order to match the description of water coverage in the bible. Basically, this isn't rain - this would be like an endless bucket of water being poured onto your head, not individual droplets, and a wooden structure such as the ark would have no chance of surviving that kind of a beating.

Combine that with problems with wood rot in the years it'd take to build it, problems with manpower and tools given known metals and crafting methods of the time, CLEAR problems with the geologic record, ice core records (many of which go back more than 10,000 years), problems with the paleontological record, human genetics (genetic markers actually provide a very clear "clock" in terms of when certain mutations arose and thus tell us when certain populations of people split off from one another - turns out, a LOT longer than 6,000 years ago), and basic intelligent thought processes....and you begin to mayyyyybe see why some MIGHT question this, eh?

But hey. Believe what you want to. Clearly no amount of readily available higher education has swayed you yet. Consider this though - if your god gave you this ability to think, reason, experiment, and question everything, why shouldn't you be able to question a religious text written over centuries by barely literate men who knew less about the world around them than the average first grade student does today? Not to mention, passages written by men born centuries or thousands of years after the events they were writing about. Don't you suppose they MAY have gotten some things wrong? Hey...I'm not saying there's no god. Honestly, I couldn't answer that - I don't have the data to say yes or no. But your god can still possibly exist even if one old book just happens to be full of crap. It could be 99% wrong, and your god could still actually exist. Proving it wrong - or questioning its content - doesn't mean anything other than you are questioning the works of fallible men and maybe your interpretation of your god is wrong - whether or not a god exists isn't the question so much as whether or not some writings are just stories. For centuries, people wrote of the giant squid as if it were myth, and yes, many stories were shown to be bollocks - but the squid itself was proven to exist. Stories can be wrong while still having some CORE elements correct - such as the existence of a creating force in the universe. Is it really so bad if only 10% of it is true? What's really important, after all, is that you have a force greater and more powerful than man can ever be to look to - not whether or not the stories related to it are all 100% true.

Question everything. If there's a god, clearly he or she gave you the ability and the brain to do so. Use that brain. Don't take a 2,000 year old book as fact without questioning it first.