The Zohar asks why God judged the world with flood of water and not fire or something else. Then explains that because the people didn’t connect lower and upper waters properly they were judged with water, which is the element related to their sins.
“וַיֹּאמֶר אֱלֹהִים, יְהִי רָקִיעַ בְּתוֹךְ הַמָּיִם, וִיהִי מַבְדִּיל, בֵּין מַיִם לָמָיִם”
“וַיַּעַשׂ אֱלֹהִים, אֶת-הָרָקִיעַ, וַיַּבְדֵּל בֵּין הַמַּיִם אֲשֶׁר מִתַּחַת לָרָקִיעַ, וּבֵין הַמַּיִם אֲשֶׁר מֵעַל לָרָקִיעַ; וַיְהִי-כֵן.”
“And God said ‘Let there be a firmament in the midst of the waters, and let it divide the waters from the waters”
7: “And God made the firmament, and divided the waters which were under the firmament from the waters which were above the firmament; and it was so.
From verse 6 we understand that the ‘waters’ filled up the entire space until God commanded the firmament to be in the midst of the water. The next verse tells the next step that was an ‘action’. We learn that from the words ‘And God MADE the firmament…’. God made actual separation in the water to make lower water, which is a female aspect and upper, which is a male aspect.
Desires that follow the purpose of Creation on the lower level create the aspect of female waters that form vessels to attract the male waters from above, restoring the original state of unified water that nourish existence.
The sin of that generation was that their desires were for the self alone and that created greater disconnection between upper and lower waters. The world became ‘dry’ of spiritual nourishments and for that reason they were judged with water.
“בִּשְׁנַת שֵׁשׁ-מֵאוֹת שָׁנָה, לְחַיֵּי-נֹחַ, בַּחֹדֶשׁ הַשֵּׁנִי, בְּשִׁבְעָה-עָשָׂר יוֹם לַחֹדֶשׁ–בַּיּוֹם הַזֶּה, נִבְקְעוּ כָּל-מַעְיְנֹת תְּהוֹם רַבָּה, וַאֲרֻבֹּת הַשָּׁמַיִם, נִפְתָּחוּ.”
“In the six hundredth year of Noah’s life, in the second month, on the seventeenth day of the month, on the same day all the fountains of the great deep burst open, and the floodgates of the sky were opened.”
The waters of the Flood came from upper and lower waters and they were boiling to match their sin that included spilling their warm seeds. That made the proper correction.