What is the meaning of the word "Nashafta"?
Rashi and Ramban #2: It means that Hashem blew. 1
Ramban #1 (citing Ibn Ezra): Hashem covered the water on the Egyptians at night-time. 2
Rashi (in Menachos, 53a), Ramban #3 and Targum Yonasan: It means Hashem blew, as if it had written 'Nashavta'. 3
Hashem caused the water to congeal with "the breath of His nostrils". Dis He now cause the water to cover them using the same breath?
Seforno and Ramban: Yes, Hashem did both actions using the same breath! 1
With the cold air that a human-being breathes through his mouth, he cools down what is hot, whereas with the hot air from his nostrils he melts what is congealed. But Hashem here did the opposite. In His anger, He breathed hot air through His nostrils, causing the water to congeal, whereas with the cold air from His mouth He caused the congealed water to melt.
What is the significance of the description "Adirim"?
Rashi (in Menachos, 53a) and Rashbam: It describes the (turbulent) water. 1
Rashi #2 (Ibid.) and Seforno: It refers to the Egyptians - and translates as "They sank like lead in the water - the Egyptians (who are described as "Adirim", or to the officers 2 [Seforno]).
Mechilta: Hakadosh-Baruch-Hu, who is called 'Adir' 3 revealed Himself to Yisrael, who are called 'Adirim,' 4 to punish the Egyptians, who are called 'Adirim' 5 to sink like lead in the water, which is described here as 'Adirim'.