“I had the thought: I wonder if anyone heard me? I dove down again and listened. Someone had. A voice, faint, plaintive yet serene, reached through the water. From maybe a hundred yards away, or a hundred miles—no way to know—but its reverberance was stirring. I went up for air, dove down and tried to imitate what I’d heard, waited, and heard a response—or was it an inquiry? A pretty dull conversation for the whale, no doubt, as I just tried to repeat what I heard, but we sustained this back-and-forth for the length of my mostly underwater, sounding swim back.”