What is the meaning of "Zoremu Mayim Avos"?
Rashi: Shechakim (a level of Shamayim) dripped a flow of thick water.
Radak: This is like it says "va'Yashkef Hashem El Machaneh Mitzrayim b'Amud Esh v'Anan" (Shemos 14:24). The thick clouds flowed water. This is the panic [that befell the Egyptians] - "va'Yaham Es Machaneh Mitzrayim" (ibid.) - they had fire, cloud water and thunder - "Kol Nasenu Shechakim."
Malbim: The verse depicts that the sea water below split via revelation of this nature in its source above - "Ra'ucha Mayim" (verse 17). Splitting below was a result of water in clouds splitting above in Igul ha'Neshimah 1 . Wind, thunder and lightning split it above, and so it split in the depths. The clouds in Igul ha'Neshimah split due to splitting in Shechakim (the highest place in Shamayim; nature does not apply there). A miraculous flow began there; it descended to the natural sky (became dressed in natural orders), and from there to the sea.
So Malbim calls the place of natural clouds formed from vapors. (PF)
Why does it say "Kol Nasenu Shechakim"?
Radak: Thunder confounded Machaneh Mitzrayim.
Malbim: Miraculous thunder in Shechakim split the water there, and from there the miracle descended and became dressed in natural orders (refer to 77:18:1:3).
What are "Chatzatzecha"?
Rashi: This is like Chitzecha (Your arrows).
Radak: They are hailstones, even though they are not mentioned in the Torah. Some say that they are the hailstones that He cast on the kings of Kena'an. And so are called small rocks of sand - "va'Yagres b'Chatzatz" (Eichah 3:16).
Malbim: Miraculous lightning in Shechakim began the miracle (refer to 77:18:2:2).
