Playful and intelligent, graceful and mysterious, whales have fascinated people for centuries. The cetacean order includes whalebone whales, such as the blue whale (the largest creature on earth), and toothed whales, such as killer whales, dolphins and porpoises. These engaging mammals were nearly hunted to extinction for their blubber, oil and meat as techniques such as harpoon guns in the 19th century and sonar tracking in the 20th century become more sophisticated. Today several species remain under threat despite an international moratorium on commercial whaling and the discovery of viable substitutes for whale products. However, a new form of tourism - whale-watching - has developed into a thriving industry that may yet offer hope for these endangered species.