Among all the floods in human records, none of them can bury a mountain as high as mount Ararat. It says that the 'flood' Noah saw may not be flood at all but a kind of catastrophe unknown to humans.
There is an impact crater on the bottom of the indian ocean that is 25 times larger than meteor crater in Arizona that dates to the approximate time of the many hundred worldwide flood stories. This would have instantly vaporized billions of metric tons of water into the atmosphere, causing a mega tsunami and a worldwide deluge of torrential rain and superstorms that would have lasted weeks and washed away every city near the shore and every inland settlement situated near rivers, streams and even dry washes in the deserts all over the earth.
Water covering the tops of mountains is just a little hyperbole that tries to convey the magnitude of the partial extinction event. In scripture "the mountains of Israel" also refers to the big shots of the community. Therefore, water covering their highest mountain could also indicate that all the well heeled big shots drowned. 10 feet of water would have done the trick, especially among desert dwellers who probably couldn't swim for a minute much less a month.. They really didn't need to exaggerate much.
Another possible explanation is that, God actually asked Noah to keep as many pairs of animals as possible such that they will be repopulated in the future world.
In the bible people are compared to lower beasts from the very first book to the very last.
If Noah took along a few pairs of lowlifes that would explain why there are still so may out there that weren't killed off in the flood.
Kangaroos are irrelevant. No one calls another person a kangaroo in any language , but they did call each other snakes, pigs, dogs, wolves, sheep, goats, rats, vultures, worms, maggots, etc., before the flood and after the flood in every language to this day..
And the book of Revelation says that there will be no sea in the future earth, perhaps that's why God never asked Noah to keep the fishes. The story has prophetic meanings which may be beyond us to understand for the moment.
The prophecy, " and there was no longer any sea" indicates that in the future world people will learn all the truth, nothing will be hidden by the mysterious deep.
This relates to the verse in Genesis that says that before there was light, the earth was without form and void, and darkness covered the face of the deep, meaning that no one knew anything about right or wrong much less the mysteries of life.
In the fullness of time, all will be revealed.