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". Does He now cause the water to cover them using the same breath?
Hadar Zekenim, Seforno and Ramban: Yes, Hashem did both actions using the same breath! 1
Hadar Zekenim: This was a great miracle. Normally, breath from the mouth is cold, and from the nose is hot. Here, His [hot] breath from the nose froze the water, and His [cold] breath from the mouth melted the frozen water..
What is the significance of the description "Adirim"?
Rashbam: It describes the (turbulent) water.
Menachos 53a: It refers to the Egyptians. 1 Ha'Kadosh Baruch Hu, who is called 'Adir' (Tehilim, 93:4) caused Yisrael, who are called 'Adirim' (Tehilim 16:3) to be paid from (punish) the Egyptians, who are called here 'Adirim', to sink like lead in the water, which is called 'Adirim' (Tehilim 93:4). 2
Seforno: It refers to the officers and heads of the Egyptian army.
Mishnah Berurah (51:17, from Pri Megadim): The note under "b'Mayim" is a Tipcha, to show that it is not connected to "Adirtm"; one must pause between them. (Some ask that likewise, there is a Tipcha under "Yoshvei", even though surely it is connected to "Pelashes" (verse 14)! Perhaps when one cannot err to expound differently, notes are assigned for other reasons (refer to 12:40:3:1*, refer to Bereishis 44:18:151:1). The Gematriya of ha'Tipcha is 103, the same as Avimelech