“He climbed the tower. Not because she asked — she had not asked, she had specifically not asked, because asking would have been an acknowledgment that she needed help, and lifeguards did not need help, lifeguards provided help, the directional flow of rescue was outward, not inward. He climbed because the tower was swaying and she was on it and the storm was worsening and his body, trained by the Navy and refined by emergency medicine, did not require permission to move toward danger.”