Each year, thousands of people fascinated by the orcas intelligence, wildness and history, embark on whale-watching cruises hoping to catch a glimpse of one. To find out more about the appeal of these gentle giants - formerly known as killer whales - Douglas Hand travelled to the Pacific Northwest, whose waters the orcas call home. There he spent some time with the people who have been closest to the whales: marine biologist and orca census-taker...