Book of Isaiah debunks Christianity, so not sure why you focus on that book, the oldest layer of Isaiah, are the verses between 40 and 55, this is older then the myth of Moses itself.
Why then does 'Red Sea' not appear anywhere in the Hebrew , only in the Septuagint, it translates as 'Red Sea', the Hebrew word for the colour Red is 'Adom , 'Red Sea', would appear in Hebrew as 'The Sea of Adam.
The Hebrew that is used is 'Suph' and according to Book of Joshua, the river was dried up, most likely drained, based on Isaiah 44:27.
Isaiah 44:27
That saith to the deep, Be dry, and I will dry up thy rivers:
Isaiah 44:28
That saith of Cyrus, He is my shepherd, and shall perform all my pleasure
The Hebrew 'the deep', is 'tsuwlah' , is similar to θάλασσα (Thalassa) meaning Sea.
Joshua 2:10
For we have heard how the LORD dried up the water of the Red sea for you,
The rivers 'dried up' , exodus states it 'parted '., which is it ?
Revelation 16:12
And the sixth angel poured out his vial upon the great river Euphrates; and the water thereof was dried up, that the way of the kings of the east might be prepared.
Revelation talks about the Fall of Babylon ( attributed to King Cyrus), then it claims the River Euphrates will dry up, to make way for the kings of the 'EAST' ( the Persian Kings)
King Cyrus did in fact dry up the River Euphrates, confirmed by Herodotus.
Herodotus 1.191
and when he came to the lake, Cyrus dealt with it and with the river just as had the Babylonian queen: drawing off the river by a canal into the lake, which was a marsh he made the stream sink until its former channel could be forded.
'Marsh, the Greek is 'ἕλος , a translation of סוּף (Suph) in 'Yam-Suph' that is mistranslated as 'Red Sea';
They you go, the origin of the parting or drying of the red sea. King Cyrus did it.