The Flood did not arrive gently. Targum Pseudo-Jonathan on Genesis 7:11 dates it with astonishing precision: the six-hundredth year of Noah's life, the second month, the seventeenth day. The Targum pauses to explain its own calendar. Until this moment the months were counted from Tishri, the beginning of the year from the completion of the world. So the second month of the old reckoning was Marcheshvan, the month of rains. The Holy One chose the month of rain to end the world with water.
Then the Targum opens a door the plain text never opens. On that day all the fountains of the great deep broke up — and the giants, the gibborim, gathered at those fountains with their sons and tried to stop them. Picture it. The waters of the deep are boiling up from below, and the towering sons of the Watchers throw themselves into the breach, trying to plug the earth like a shattered dam. They fail. The windows of heaven open above them, and the Flood comes at them from both directions at once.
This is the Targum's mythic signature. The giants, those half-angelic rebels the earth had groaned under for centuries, meet their end at the very fountains they tried to seal. Strength against the Creator is strength thrown into a fire. The takeaway, as the old darshanim tell it: when the Holy One opens both the deep and the sky, there is no wall anyone can build between them.