This chapter provides an introduction to the book ‘Ocean Governance (Beyond) Borders’, a text that that shifts across varying oceanic terrains to offer, in one collection, a sustained reflection on bordering and oceans, written by those central to researching and reflecting on such debates. The chapter reviews some of the longstanding literature on borders, boundaries and enclosures from across different disciplines, including human geography and international relations, before examining such ideas in the particular context of the seas and oceans. It provides a backdrop to the ways borders are planned, enacted, monitored and enforced but also the ways in which they are porous, leaky, subject to change, transgressed and contested, all in a largely mobile medium—the seas and oceans—that are ever resistant to bordering. The chapter offers a discussion of (en)closures as a means of opening up debates central to the book, to introduce the key themes that weave through the chapters, as well as briefly summarizing the chapters that comprise the collection. The chapter ends with ideas to frame readers’ engagement with the book, and some thoughts on how the contributions herein might be navigated.