Mishnayos Yevamos Perek 16 Mishnah 4

If a man fell into the water and did not come out, whether the body of water has a visible end or does not have a visible end, his wife is prohibited from remarrying. There is no absolute proof that the man died, as it is possible that he emerged from the water some distance away. Rabbi Meir said: An incident occurred involving a certain person who fell into the Great Cistern and emerged only after three days. This is evidence that sometimes one may survive a fall into water, even when everyone assumes he is dead. Rabbi Yosei said: An incident occurred involving a blind man who descended to immerse for ritual purity in a cave, and his guide descended after him, and they disappeared there, and they remained there long enough for their souls to have departed, and the Sages permitted their wives to marry because they had disappeared into the water and not emerged. And there was another incident in Asya in which they lowered a certain man into the sea on a rope, and when they pulled the rope back to land only his leg came up in their hands, and they were not certain whether he was alive or dead. The Sages said: If his leg was cut from the knee and above, his wife may marry, as he did not survive such a wound; if his leg was cut only from the knee and below, she may not marry.

נָפַל לְמַיִם, בֵּין שֶׁיֵּשׁ לָהֶן סוֹף, בֵּין שֶׁאֵין לָהֶן סוֹף, אִשְׁתּוֹ אֲסוּרָה. אָמַר רַבִּי מֵאִיר, מַעֲשֶׂה בְאֶחָד שֶׁנָּפַל לְבוֹר הַגָּדוֹל, וְעָלָה לְאַחַר שְׁלֹשָׁה יָמִים. אָמַר רַבִּי יוֹסֵי, מַעֲשֶׂה בְסוּמָא שֶׁיָּרַד לִטְבֹּל בִּמְעָרָה, וְיָרַד מוֹשְׁכוֹ אַחֲרָיו, וְשָׁהוּ כְדֵי שֶׁתֵּצֵא נַפְשָׁם, וְהִשִּׂיאוּ נְשׁוֹתֵיהֶם. וְשׁוּב מַעֲשֶׂה בְעַסְיָא בְּאֶחָד שֶׁשִּׁלְשְׁלוּהוּ לַיָּם, וְלֹא עָלָה בְיָדָם אֶלָּא רַגְלוֹ, אָמְרוּ חֲכָמִים, מִן הָאַרְכֻּבָּה וּלְמַעְלָה, תִּנָּשֵׂא. מִן הָאַרְכֻּבָּה וּלְמַטָּה, לֹא תִנָּשֵׂא: