Just as the unprepared were destroyed by the Flood, so also, the unprepared will be overtaken with destruction when Jesus returns in glory. 

Jesus compared the final years before the “coming of the Son of Man” to the period leading up to the Great Flood. “As it was in the days of Noah, so shall it be.” Some take this as a prediction of a return to the same conditions that existed in Noah’s time, the repetition of the moral anarchy and violence that prompted God to send the floodwaters. The final days will be marked by chaos and catastrophes.