From the surface of the ocean, it's hard to see any visible signs of life below. But this remarkable ecosystem is teeming with life--life that is increasingly under environmental stress. And it is often the predators that sound the earliest warning signs. By tracking a wide variety of ocean predators, the Tagging of Pacific Predators (TOPP) project provides essential cutting-edge information about the state of the ocean's health and the challenges facing all its inhabitants.