וַיָּבֹ֧אוּ בְנֵֽי־יִשְׂרָאֵ֛ל בְּת֥וֹךְ הַיָּ֖ם בַּיַּבָּשָׁ֑ה וְהַמַּ֤יִם לָהֶם֙ חֹמָ֔ה מִֽימִינָ֖ם וּמִשְּׂמֹאלָֽם׃
以色列人進入海中，走在乾地上；水在他們的左右兩邊，成了他們的牆。
Sforno
הלכו ביבשה, seeing the deep parts under the sea had all become frozen from the east wind so that the Israelites were crossing on frozen mud.
Or HaChaim
בתוך הים ביבשה, in the midst of the sea on dry land. The words "in the midst of the sea" mean in the inner part of (what had formerly been) the sea; the word ביבשה means that the sea bed was not muddy but completely dry.
Rabbeinu Bahya
ויבאו בני ישראל בתוך הים ביבשה, ”the Children of Israel came into the sea when it was dry land.” The plain meaning of these words is that the place which had previously been sea was now dry land.