The flood of Noah is the one most destructive act in the history of the earth. And it was brought on by a just, righteous, almighty God. When we study the Bible in the Old and New Testament we find that Noah's flood instructs us on how God desires us to live if we are to be with Him, and not against Him. Let's take a quick look:

1. When did Noah's flood happen? Although the exact year is disputed, we know it happened after the descendants of Adam and Eve had lived some time, and before Abraham was born.
2. Why did God flood the earth? Because of the wickedness of mankind on earth. It grieved God's heart, and God was sorry He made mankind. (Gen 6:5-7)
3. What was God's goal with the flood of Noah? To completely wipe out all corrupted living things on the face of the earth, EXCEPT Noah and his family (8 humans) and the living creatures that were on the ark of all shapes and sizes. (Gen 6:7, Gen 7:4, Gen 7:21,  Gen 7:22, Gen 7:23)
4. How did God bring about the flood? With "The fountains of the great deep bursting forth, and the windows of heaven being opened."
5. Why did God choose Noah to survive and all humans since be his heirs? Because Noah was a righteous man and walked with God. (Gen 6:9)

It is hard to imagine God doing this. And some people even dispute the claims of it's accuracy or ability to happening. Yet, a deeper dive into the Hebrew words being used in these verses as well as in Genesis chapter 1 when God created the heavens and the earth you would find that it is all very possible and real. For more information, you can check out Biblehub.com and search for the Hebrew word numbers 699 (windows), 7549 (firmament), 8064 (heaven), 1234 (burst open). They all help color in the image of what was actually happening during the flood.

But the important take away is not only did God destroy everything on earth except 8 humans and many creatures. But that God provided a WAY for mankind to live in right relationship with God. By "walking with God" as Noah did, we can show the righteousness that God desires from us. In the New Testament, Jesus calls us to "take up our cross and follow Him" (walk with him). We need only to confess with our mouth that Jesus is Lord and believe in our hearts that God raised Him from the dead, and we will be saved (Rom 10:9). That's it. That is how we can enter the modern day ark and be saved.