By the time of Noah, there were not enough people to require a worldwide flood. People were also not populated in one region to require a local flood.
It is estimated that 12 to 15 generations had been born on Earth by the time of the Flood.
Noah was the 9th generation from Adam.
Easily, there could have been one billion people alive by Noah's 600th birthday.

LOCAL FLOOD THEORY
You cannot cover the highest mountains with water for several months if the flood was only regional.
Secondly, and even more significant, is the covenant which God made after the Flood. God promised, "Never again shall there be a flood to destroy the Earth".

If the Flood of Noah was merely a local flood, then God would have broken that promise hundreds of times since then because there have been a lots of regional floods after Noah's Floods.

A population of one billion would not be likely contained within a single valley that would be amenable to local flooding.

Nothing would have kept the people, birds and all the animals confined within that local flood area.

If God wanted to destroy a local area, HE would have instructed Noah and his family to migrate to another area.

WORLDWIDE FLOOD THEORY
There are 30 million different species of animals on Earth. With both males and females needed for their survival, Noah had to get 60 million of them into the Ark and make sure not even a single animal dies on the Ark during the flooding period.
Noah and his family could not have travelled to all lands and caught all those animals.

The animals could not have travelled to the Ark because of natural barriers like high mountains, rivers and seas.

The Ark was not big enough to hold all those animals and carry enough food for a year.

According to calculations, the Ark could hold the equivalent of 522 standard two-decked railroad stock cars. To carry no more than 35 000 estimated individual vertebrate animals, the average size being that of a sheep, would require no more than 146 such railroad cars.

The Ark could not have carried enough fresh water for a year.
If we assume that the ocean's salt content was the same as today, then the excess Flood water likely diluted it sufficiently for drinking. Saltwater fish could not have survived in fresh water or less salty water.

There would not be enough oxygen for them at the high altitude, at the peak of the flood. Atmopheric pressure and oxygen concentrations are relative to sea level.

NOTE:
It rained for 40 days but Noah and his family, and all the animals, spent 365 days on the Ark waiting for the land to dry.
It is highly possible that some of the animals had already reproduced and multiplied their population because some animals have a lifespan of less than a year. So in order for them to survive they had to reproduce.

CONCLUSION
The Ark needed no means of propulsion or steering. There was no particular place it needed to go.
After exposing the land to the incredible Flood waters, it is unlikely that Noah's family could have recognised any landmarks after the Flood.
You can imagine how long, after the Flood, it took them to plant and cultivate another food. They must have had more than a year's groceries on the Ark.
There is not enough evidence that the whole Earth was under water.
We cannot be sure what the Earth's geography looked like prior to the Flood.

If the "Local Flood Theory" is unlikely and "Worldwide Flood Theory" even more unlikely, the question is...

DID THE NOAH'S FLOODS REALLY EVER HAPPEN?

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