The Bible puts a great deal of emphasis on the historical reality of the Great Flood, referring to both the flood and to Noah multiple times.
The record in Genesis tells us that the world became so wicked God's wrath was poured out in the waters of the flood upon everyone, but eight persons. "And GOD saw that the wickedness of man was great in the earth, and that every imagination of the thoughts of his heart was only evil continually" (Genesis 6:5). The reality of the Flood is confirmed in planet-wide geological and fossil evidence. So God passed judgment on sinners on a scale that staggers the comprehension, and then left marks of the event all over the earth, along with a written record in the Bible.
In the New Testament this is cited to remind people of God's fearful wrath against sinners. "And spared not the old world, but saved Noah the eighth person, a preacher of righteousness, bringing in the flood upon the world of the ungodly" (II Peter 2:5). The subject of God's wrath today is avoided, evaded, mocked, argued with, and denied. Nevertheless, God will not be shouted down, and according to Romans, "the wrath of God is revealed from heaven..." (Romans 1:18). For God to have shown so clearly His wrath against sin leaves us all guilty and without excuse.
The Bible also tells us that our present time will lapse into a worldwide practice of sin on a scale comparable to the conditions preceding the Great Flood. "But as the days of Noe were, so shall also the coming of the Son of man be" (Matthew 24:37). God's solution to deteriorating conditions in our time will be the Second Coming of His Son to destroy His enemies as described in Revelation.
Before that time, we are commended to the example of Noah and his preparation for the never-seen-before calamity. He escaped God's wrath by taking the warning seriously and trusting himself to the provision for safety prescribed by God. Our provision today is not a large boat, but a great Saviour, Jesus Christ who came the first time to die and rise again that He might be the saviour from sin for all that receive Him by faith.