The last case of the Mishna discusses a case where a person drowned and they found his foot. The judged that if it was above the knee we assume he died and the lady is permitted to get married below the foot since he could still live maybe he got out of the water someplace else. I was wondering how they wer so sure it was his foot? Was there a "siman"? Did they assume that since he went into the water there and they found the foot it was probaly his? If so maybe the foot was from someone else and it flowed there?