From gray whales plying the waters of Baja California to acrobatic manta rays in the Maldives and parading penguins in Antarctica, National Geographic photographer Thomas Peschak has spent a lifetime documenting the beauty and fragility of underwater life and the majesty of wild coastlines. In the 200 color images here, Peschak photographs sharks in a feeding frenzy, tracks sea turtles the size of bears, and dodges marine poachers, to reveal the splendor of pristine seas as well as the dark side of pollution, overfishing, and climate change.