"And Israel saw the Egyptians dead" (Exodus 14:30). For four reasons Israel saw the Egyptians dead: so that Israel would not say, "Just as we have come up on this side, so too have the Egyptians come up on that side"; and so that the Egyptians would not be saying, "Just as we are lost in the sea, so too are Israel lost in the sea"; and so that Israel would take the spoil, for the Egyptians were laden with silver and gold and precious stones and pearls; and so that Israel would set their eyes upon them and recognize them and rebuke them. As it is said, "I will rebuke you and set the case before your eyes" (Psalms 50:21), and, "My enemy will see it, and shame will cover her" (Micah 7:10). "And Israel saw the Egyptians." It does not say "dead" in the plural but "dead" in the singular - dead and yet not dead [i.e. on the point of death]. This is like the matter of which it is said, "And it came to pass, as her soul was departing, for she died" (Genesis 35:18). And was she truly dead at that moment? Rather, dying and not yet dead.
Four Reasons Israel Saw the Egyptians Dead Upon the Shore
Yalkut Shimoni on Torah 239:2
וַיַּרְא יִשְׂרָאֵל אֶת מִצְרַיִם מֵת. מִפְּנֵי אַרְבָּעָה דְּבָרִים רָאוּ יִשְׂרָאֵל אֶת מִצְרַיִם מֵתִים, כְּדֵי שֶׁלֹּא יֹאמְרוּ כְּשֵׁם שֶׁעָלִינוּ מִצַּד זֶה כָּךְ עָלוּ מִצְרַיִם מִצַּד זֶה, וּכְדֵי שֶׁלֹּא יְהוּ מִצְרַיִם אוֹמְרִים כְּשֵׁם שֶׁאָנוּ אֲבוּדִים בַּיָּם כָּךְ אָבְדוּ יִשְׂרָאֵל בַּיָּם, וּכְדֵי שֶׁיִּקְחוּ יִשְׂרָאֵל אֶת הַבִּזָּה שֶׁהָיוּ טְעוּנִין כֶּסֶף וְזָהָב וַאֲבָנִים טוֹבוֹת וּמַרְגָּלִיּוֹת, וּכְדֵי שֶׁיְּהוּ יִשְׂרָאֵל נוֹתְנִין אֶת עֵינֵיהֶם בָּהֶן וּמַכִּירִין אוֹתָן וּמוֹכִיחִין אוֹתָן, שֶׁנֶּאֱמַר (תהלים נ, כא) "אוֹכִיחֲךָ וְאֶעֶרְכָה לְעֵינֶיךָ" (מיכה ז, י) "וְתֵרֶא אֹיַבְתִּי וּתְכַסֶּהָ בוּשָׁה". וַיַרְא יִשְׂרָאֵל אֶת מִצְרַיִם. מֵתִים אֵינוֹ אוֹמֵר אֶלָּא מֵת, מֵתִים וְלֹא מֵתִים כָּעִנְיָן שֶׁנֶּאֱמַר (בראשית לה, יח) "וַיְהִי בְּצֵאת נַפְשָׁהּ כִּי מֵתָה", וְכִי מֵתָה הָיְתָה, אֶלָּא מֵתָה וְלֹא מֵתָה.