Yevamos 16:4-5

Yevamos 16:4

If a man falls into the water, his wife may not re-marry (because he may still be alive); this is so whether or not one can see the other shore. Rabbi Meir reported an incident in which a man once fell into the reservoir and turned up three days later. Rabbi Yosi reported an incident in which a blind man went with a guide to immerse in a cave. They were gone long enough to be presumed dead so the Sages allowed their wives to re-marry. Furthermore, an incident occurred in Asya in which they lowered someone into the sea and only his leg came back up. The Sages said that if it was severed above the knee, his wife may re-marry but if below the knee, she may not.

Yevamos 16:5

If one overhears women discussing a person’s death, it is sufficient to testify that he died. Rabbi Yehuda says this is also true if one hears children saying that they are going to this person’s funeral. This is true whether or not one is aware of the legal impact of his statement. Rabbi Yehuda ben Bava says that such a statement is only accepted from a Jew if he intends it as testimony but if a non-Jew intends it as testimony, it is not accepted.