Is Genesis supposed to be taken literally? Peter certainly thought so. In his God-guided second epistle, Peter warned of a time when people would be deliberately ignorant of the fact that God created the earth out of water, and destroyed it with a global flood. Fast forward to the modern day, many Christians might as well have this verse tattooed on their foreheads as a warning label. There are many who do not accept that the flood was a global one, if they even acknowledge that it happened at all.
But it did happen, and it was global. But there's more to Peter's epistle than just to say "people will ignore the flood". Peter continued to speak about a second global judgement. A judgement not by water, but by fire (verse 7). God is patient enough to hold off on that judgement for quite some time, but a time is coming when God will once again destroy the wicked completely. It is this that Christians are working towards. We may well be saved. The only question we have to ask about this judgement is how great will our reward be on the other side (1 Corinthians 3:9-15). But just as those around Noah perished, so also will those around us perish. Unless we give them the Gospel.
The exact time of the return of Jesus is unknown. Where many have tried to predict it, all have failed, and will continue to fail. Jesus could come back to judge the earth tomorrow, or in a thousand years from now. We don't know. For this reason, we ought to be full time missionaries. With a great sense of urgency, let us constantly be looking for ways to build God's Kingdom.