Historians have been slow to incorporate the ocean as a focus of study, in part because we have viewed it as standing mostly apart from human societies and activities. Whether that was ever truly the case is arguable, but it is certainly no longer true today. Global climate change and ocean acidification point to the now-pervasive impact of humans on the ocean environment and, conversely, the crucial importance of the ocean in the development of human affairs. Understanding the human effects on the ocean will remain mainly the preserve of natural scientists, but understanding the origins, development, and repercussions of those impacts is a job for historians and other social scientists. © 2014 by The History of Science Society. All rights reserved.