To show that that the Global Deluge or Noachian Flood happened, here are some details to consider: First, at Genesis 1:2, it says that "the earth was formless and desolate, and there was darkness upon the surface of the watery deep, and God’s active force was moving about over the surface of the waters."(Note: God's personal name is Jehovah, Isa 26:4)
Before the creation of life on the earth, the earth was initially covered with water. Then, at Genesis 1:6-8, as the earth was being prepared for life, it says: "Then God said: “Let there be an expanse (or atmosphere) between the waters, and let there be a division between the waters and the waters.” Then God went on to make the expanse and divided the waters beneath the expanse from the waters above the expanse. And it was so. God called the expanse Heaven. And there was evening and there was morning, a second day."
So, Jehovah God lifted the massive amount of water that covered the earth above the "expanse" or heaven, being like a thermal blanket that would make the entire earth comfortably warm year round, so that the waters would have been placed at the outer layer of the atmosphere as a barrier, like the the windows of a car rolled up on a sunny day, so that heat would be retained and not lost.
Genesis 1:7, 8 now states: "Then God went on to make the expanse (or atmosphere [that has now been divided into five distinct layers] and also called "the heavens" where birds fly, Gen 1:28) and divided the waters beneath the expanse (into Seas or shallow bodies of water, Gen 1:10) from the waters above the expanse. And it was so. God called the expanse Heaven. And there an evening and there was a morning, a second day".
So, from the 2nd "creative" day till 1,656 years into the 7th "creative" or Jehovah's "rest" day, the waters were suspended above the earth, or for some 36,000 years.(Note: each "creative" day was not 24 hours that the churches of Christendom have taught, but were about 7,000 years long, see Heb 4:1-5, whereby the 7th "creative" day was still ongoing some 4,000 years after it began)
Being that most of the "waters" that completely covered the earth were lifted above the earth (with the exception of those left remaining to be the Seas) to act like a warm blanket or "hot house", this kept in the warmth of the sun so that green plants grew everywhere on the earth, even in what is now called the polar regions.(Note: even when the temperature is cold outside, sun shining through a hot house's glass can keep it warm)
Fossilized pollen and spores have been recovered from seabed sediment in Antarctica that reveals that it once supported palms and near-tropical forests, showing that temperatures at the poles were not vastly different from those at the equator.(Note: though the "waters" were massive in amount [and are what now constitutes the oceans], the "waters" could easily be seen through because they were in a hot vaporous state)
For example, many frozen mammoths have been found in Siberia, in the permafrost. One such mammoth (Beresovka mammoth that was shipped back to St Petersburg, Russia, some 3,700 miles away from where it was located) was found in 1901 with "green" buttercups in it's mouth and stomach, thus indicating that it was frozen while still grazing in a warm climate.
Another example of the global deluge is that over 500 fossilized giant oysters, some with a circumference of up to 11 feet [3.5 m] and weighing up to 650 pounds [300 kg], were found in Acostambo, Peru, at an elevation of 12,300 feet [3,750 m] above sea level in 2001 in the Andes mountains.(newspaper El Comercio)
Paleontologist Arturo Vildozola found the oysters just a few meters from a highway that runs between the towns of Pampas and Colcabama, but nobody paid any attention to them. Thus, what was once a sea bed became a mountain because of the global flood, whereby Jehovah God buckled the mantle of the earth so that mountains rose, allowing land to be above the "waters".(see Ps 104:5-9)
In 2370 B.C.E., God caused the "waters above the expanse" to suddenly drop down to the earth.(Gen 1:7) In so doing, this caused a cataclysmic atmospheric change. Imagine being in place where the "outside" temperature is about -454 degrees F. (or "outer space") and then suddenly losing protection from the cold, along with powerful hurricane force winds that causes the windchill to "feel" like even colder temperatures.(Note: with a temperature of -45 F. and 60 mph winds, the windchill factor is -98 F.; also note: in -70 F. hot water, when thrown into the air, freezes almost instantly, often called the Mpemba effect, as opposed to cooler water that takes much longer to freeze, though scientists have yet to satisfactorily explain why)
The sudden change in temperature would cause even the most "stout-hearted" or warm-bloodied life to freeze, for temperatures would plummet "like a rock". Animals around the earth that were living in tropical conditions were now subjected to "quick freeze", especially at the poles, for the "waters above the expanse" came in heavy sheets of rain during the Global Deluge, so that temperatures plunged so rapidly at or near the poles (or within the Arctic Circle) they became frozen almost instantly, that what was once a temperate zone where animals of all types thrived now suddenly became a frozen "wasteland".(Gen 7:6)
The waters that now make up the oceans were once suspended above the earth and were called "the heavenly ocean"or Hebrew ham mab bul at Genesis 6:17. Hence, the evidence for a Global Deluge is sound, but there will be those who will cast doubt no matter how much evidence is presented, for they are as David wrote at Psalms 10: "For the wicked one boasts about his selfish desires......He disrespects Jehovah. In his haughtiness, the wicked man makes no investigation; All his thoughts are: “There is no God.”(Ps 10:3, 4)
In speaking about "the days of Noah", Jesus used them as a backdrop concerning the "great tribulation" that will end the "last days" (2 Tim 3:1), telling four of his apostles: "Concerning that day and hour (as to when the great tribulation will occur exactly) nobody knows, neither the angels of the heavens nor the Son, but only the Father. For just as the days of Noah were, so the (invisible) presence of the Son of man will be. For as they were in those days before the Flood, eating and drinking, men marrying and women being given in marriage, until the day that Noah entered into the ark, and they took no note until the Flood came and swept them all away, so the (invisible) presence of the Son of man will be.”(Matt 24:36-39)
Likewise today, very few are aware as to when the “last days” began (as well as Jesus invisible “presence” in 1914, see Rev 6:1-8) and how close we are to the “great tribulation”, whereby only those who “calls on the name of Jehovah will be saved”.(Rom 10:13)