In parshat Noach, perek 7, pasuk 23, The opening word "וַיִּמַח" is presented as an active verb, attested to by the presence of the word אֶת (I am summarizing the discussion of rashi and the Sapperstein explanation, driven by the lack of a dagesh in the mem).
כג וַיִּמַח אֶת-כָּל-הַיְקוּם אֲשֶׁר עַל-פְּנֵי הָאֲדָמָה, מֵאָדָם עַד-בְּהֵמָה עַד-רֶמֶשׂ וְעַד-עוֹף הַשָּׁמַיִם, וַיִּמָּחוּ, מִן-הָאָרֶץ; וַיִּשָּׁאֶר אַךְ-נֹחַ וַאֲשֶׁר אִתּוֹ, בַּתֵּבָה
The ramban, when he discusses this section of the pasuk uses the idea in the passive, as it is used further on in the pasuk.
In fact, from pasuk 17 and on, the opening verbs are either in the active form with an initially explicit subject - "hamayim" or "hateivah" (as in וַיִּרְבּוּ הַמַּיִם, וַיִּשְׂאוּ אֶת-הַתֵּבָה, וַתָּרָם, מֵעַל הָאָרֶץ. יח וַיִּגְבְּרוּ הַמַּיִם וַיִּרְבּוּ מְאֹד, עַל-הָאָרֶץ; וַתֵּלֶךְ הַתֵּבָה, עַל-פְּנֵי הַמָּיִם) or in the passive (וַיְכֻסּוּ, וַיִּגְוַע). In this pasuk, though, there seems to be an importance to the fact that the verb is active and yet no subject is listed. If it has been in the passive (either with or without the אֶת), it would have made perfect and consistent sense. Does anyone have any insight as to why this choice of the unattributed active might be? I can understand not wanting to attribute erasing mankind to the water which was just a proxy for hashem and thus making the verb singular, but then why not say "elokim" in the beginning of 23?