I was halfway to the nine-foot end of the pool at my neighborhood Y when a middle-aged man in the adjacent slow lane, quickly crossed over into my lane and began swimming towards me. We were about to collide, but when I saw him approaching, I immediately uprighted myself and started treading water. When he finally saw me, he asked, “What’s wrong? Why did you stop?” and then swam around me, oblivious to the danger he nearly caused. At that moment, I turned around, certain that Lila, one of the lifeguards on duty, had seen what had happened, knowing she would speak to the man. “I saw it,” the young girl said, easing her way down the steps of the metal lifeguard chair, red flotation raft slung across her chest. She walked purposefully to the edge of the three-foot end, blew her whistle, and beckoned to the man, who, now…