What does the Torah mean when it writes "u'Mitzrayim Nasim Likraso"?
Rashi: Refer to 4:24:4:1*.
Seforno: The moment Hashem began to wreck havoc with them (from the beginning of the morning watch), they turned around and fled in the direction of the opening through which they had entered the channel; they continued to flee until dawn-break, when Hashem sent the water crashing down upon them, at which point they were fleeing towards the oncoming water.
Rashbam: After trying unsuccessfully to turn their wheels in the opposite direction to flee, 1 they finally succeeded, just as the water began to crash down upon them, and they found themselves facing the oncoming water.
Targum Onkelos: It means that Mitzrayim was fleeing from before it.
And what are the ramifications of the phrase "Va'yena'er Hashem ... be'Soch ha'Yam"?
Seforno: Hashem emptied (shook) them from their chariots to the bottom of the sea. 3
Targum Yonasan: Hashem gave them the strength 4 to withstand the suffering that they were going through, in order to receive the punishment that they deserved (for their cruel subjugation of Yisrael.