Despite the fact that the vast majority of the earth's surface is made up of oceans, there has been surprisingly little work by geographers which critically examines ocean-space, our knowledge and perceptions of it. This book sets up a broad conceptual and methodological framework through which to analyse specific events that contributed to the production of geographical knowledge about the ocean, and then discusses this knowledge production. Such events to be discussed include (but are not limited to) Christopher Columbus' first transatlantic journey, the mapping of nonexistent islands, the establishment of transoceanic trade routes, the discovery of large-scale water movements, the HMS Challenger expedition, the search for the elusive Terra Australis Incognita, the formulation of the theory of continental drift and the mapping of the seabed. Using a combination of original, empirical (archival, material and cartographic), and theoretical sources, these events are analysed and, in doing so, it uniquely brings together fascinating specific stories from throughout history with a broad overview of the production of geographical knowledge about the ocean. It questions how we know what we know about the oceans, and how this knowledge is represented and mapped. The books then uses this representation and mapping of geographical knowledge as a way coherently tracing the evolution of oceanic spatial awareness. In recent years, particularly in historical geography, discovering and knowing the ocean-space has been a completely separate enterprise from discovering and colonising the lands beyond it, and as there has been such focus on studying colonised lands, the oceans between them have been neglected. This book gives the geographical ocean a voice to be acknowledged as a space where history, geography and indeed historical geography took place.