Here is a true story from the book "Angels of God" by Mike Aquilina :

A friend of mine, a noted Harvard-trained philosopher, was an unbeliever as a young man. One day he was swimming in the ocean, and the undertow swept him away. He knew he was drowning, with no hope of rescue, when suddenly a strong arm grabbed him and towed him to shore. His rescuer was a big muscle-bound guy. When my sputtering friend tried to thank him, the guy laughed at him—and then vanished. This marked a milestone on my friend's road to conversion.