Where was Moshe standing, when Hashem instructed him to raise his hand over the sea?
Rashbam: He was standing on the sea-bank, after he and all Yisrael had all crossed to the other side.
Why does Hashem punish the wicked with water specifically? (We find this by the generations of Enosh and the Flood as well.)
Maharal #1 (Gevuros Hashem Ch. 14, p. 70): The terms "Beri'ah" and "Yetzirah" are not used in Bereishis regarding water. Water is fluid and lacks defined form (Tzurah). Hashem created the world for His glory -- to be brought about primarily through man, who possesses Tzurah. When man misuses his high level, and sins, then Hashem is glorified [through punishing the wicked] by means of water, which lacks Tzurah. 1
Maharal #2 (ibid. Ch. 59, p. 261): Significantly, the very same material that had been negated before Bnei Yisrael, was now activated to wipe out their enemies. 2
See 14:15:4:1 ; it was the Chomer (material) nature of water that split before Bnei Yisrael. Also refer to Bereishis 6:17:1.1 ; and Bereishis 7:11:3.1 .
How could the Egyptians have been punished with water? Wasn't this against Hashem's oath not to bring another flood (see Rashi to Shemos 1:10)?
Maharal #1 (Gevuros Hashem Ch. 14, p. 70): See Sotah 11a, and Shemos Rabah (to Shemos 1:10). As Maharal explains - Hashem's oath was not to flood the world as a whole. It did not preclude punishing individual people, or even nations.
Maharal #2 (ibid.): The oath was not to allow the waters to overpower other creations (i.e., and overrun the dry land). The Egyptians, however, were (lured and) thrown into the sea, which is comparable to any other punishment.
QUESTIONS ON RASHI
Rashi writes: "And the water shall return - [I.e.,] the waters that are [now] standing upright like a wall, will return to their place...." What is Rashi explaining?
