"Humpback on the starboard side,” shouts First Mate Kevin, sticking his head down the companionway from the bridge of the motor vessel Aurora Explorer. I grab my camera and leap up from the lunch table. In half-a-dozen steps, I’m through the back door of the main cabin and poised for a shot just as the last tip of a massive tailfin slips out of sight, leaving only a neatly expanding circle on the surface of the sea. I wait a few minutes in case the whale resurfaces within range, but I’m not disappointed when it doesn’t. I already have one good tail shot.