What is the validity of the claim that a man who saves a woman from drowning becomes a mahram (a relative one may not marry) to her?

Question:
He says: Honorable Shaykh, may Allah grant you success, some of the common people believe that a man who saves a woman from drowning becomes her brother, and she greets him with the salam. Is this correct?

Answer:
No, this is invalid. This is a popular opinion. He is not a mahram to her. Mahram status is established only through kinship, breastfeeding, or marriage, one of these three things: either by kinship, or by breastfeeding, or by marriage. As for if he saves her from destruction, he is a stranger to her, and she is a stranger to him. Yes.