"Exactly how did Noah fit millions of animals on a boat?" He didn't fit "millions" on the Ark, only about 2,000 kinds were needed. Make the wrong presumption, you will almost always get the wrong answer. Like you actually think Christians are "indoctrinated" by reading a book? Then why aren't you "indoctrinated"? Irrational thinking gets you nowhere.
Over one million animal species have been named, but it’s a mistake to assume all were on the Ark. The Bible says Noah took only air-breathing land animals. So that excludes sea creatures and possibly insects and other invertebrates.
Of the land vertebrates, there are only around 33,000 named living species (and a few thousand more fossil species). These are divided into fewer than 10,000 genera and 1,000 families.
Students in vertebrate paleontology at Liberty University are still finalizing the list of extinct families and living families. So far, the current estimate of living and extinct vertebrate families is about 950, but I gave you a conservative estimate of 16,000 from an older study.
So how many kinds of animals were on the Ark? The answer depends on which modern taxonomic level—order, family, genus, or species—represents each original “kind.” Two times 1,000 gives about 2,000 land-dwelling vertebrate animals that Noah had to care for.
Without tiering of cages, only about half of the Ark floor would have been necessary to house all of the animals required on the Ark and these could all fit on one level (out of three levels). What’s more, many could have been housed in groups, which would have further reduced the required space, leaving enough room for a large play pen as big as a tennis court.
They had decades to prepare for this journey and likely were saving seeds and growing food in planters and pots to transport to the Ark. The upper deck could easily accommodate a large garden.
The dimensions of the Ark are convincing for two reasons: the proportions are like that of a modern cargo ship, and it is about as large as a wooden ship can be built. The dimensions are less than half the Titanic or Queen Mary.
There were large wooden ships of similar length built with the same level of technology in ancient times in far less time: The Greek Tessarakonteres 200 BC 420' x 52'.
The Bible does not tell us that Noah and his sons built the Ark by themselves. Noah could have hired skilled laborers or had relatives, such as Methuselah and Lamech, help build the vessel. However, nothing indicates that they could not—or that they did not—build the Ark themselves in the time allotted.
If one or two men today can erect a large house in just 12 weeks, how much more could three or four men do in a few years? Adam’s descendants were making complex musical instruments, forging metal, and building cities—their tools, machines, and techniques were not primitive. The idea that more primitive civilizations are further back in time is an evolutionary concept.
When you stick to the facts instead of unfounded, unsupported OPINION, Noah's Ark is entirely possible.
The Flood itself reveals innumerable facts in evidence in historical records, visible stratigraphy and fossils.
Parallel historical accounts of Noah's Flood are found in the records of more than 500 civilizations around the world, many with no clear connection. Independent from the Bible, Noah's grandson Kush is specifically named as a post flood king in the Sumerian Kings list.
Then you have non-textual physical lines of evidence indicating a global event about the time (based on genealogies) that are consistent with the flood or the likely aftermath. The "fossil bloom" in the Cretaceous Period of geologic time screams Noah's Flood, corroborates and verifies the Bible, a "bloom" of evidence everywhere of Noah's Flood in stratigraphy, fossils of billions of dead things piled on top of each other.
Hmm, clear evidence of a catastrophic flood in recorded history of over 500 civilizations, evidence of a bloom of fossils, evidence of tortuous, catastrophic pancake layers of sediment like the Tapeats covering the entire North American Continent, the Sauk layer covering two-thirds of the Earth, clear evidence of a greater Flood that laid down these hundreds and thousands of feet of sediment across the planet, evidence of plate tectonics movement and shifting of the Earth's crust (much greater than today), then comes the evidence of a bloom of humanity, what more clear evidences of the Bible corroborated in reality can be ignored when the burden of proof of the scientific method has been met? Science confirms the Bible, not evolution.
Then in one generation not one but at least two and arguably three advanced civilizations (might that be from Shem, Ham, and Japheth?--Noah's sons) complete with language, writing, irrigation, monuments, domestication of beasts of burden, a monetary system, a system civil and criminal law.. Poof like magic just suddenly there. Civilization and humanity began again after Noah's Flood, right where the Bible says, exactly when written language appears out of nowhere about 2300 BC, with no clearly identifiable precursors.
If we count the generations back to Noah, it would be about 150. The Flood was roughly 4,500 years ago. Average generation span of 30 years. Divide 30 into 450, and you get 150 generations. Sure, it's a rough estimate, coincidence that it's so accurate (like most of the Bible)?
Why is there no historical support for Noah and his flood or for the entire story of Exodus?
http://plottingeoe.com/blog/why-is-there-no-historical-support-for-noah-s-flood-or-for-the-entire-story-of-exodus
How sure are we the Earth is 4.543 billion years old and not 6,000 years old?
http://plottingeoe.com/blog/how-sure-are-we-the-earth-is-4-543-billion-years-old-and-not-6-000-years-old
Is Noah's Ark a Fairytale?
Why don't Christian fundamentalist just give and admit that Noah the Ark is just a made up fairytale?
http://plottingeoe.com/blog/is-noah-s-ark-a-fairytale
Dating the Bible w Egypt pyramids and Gilgamesh (also ice cores)
Did The Biblical Flood Happen?
http://plottingeoe.com/blog/did-the-biblical-flood-happen
Geology of Grand Canyon & Noah's Flood
In what ways do you justify that the Earth is some 6000 years old?
http://plottingeoe.com/blog/geology-of-grand-canyon-noah-s-flood