This article examines the role of the sea in international law. The sea is a feature in several significant ways in international law, both in its history and its present. I argue that international law has developed its spatial elements in response to a perception of the ocean as a blank and empty space. This perspective is incorrect. The sea is not empty, but its spatiality is unfamiliar. The article explores other understandings of the sea, in an attempt both to correct this, but also to challenge the dominant construction of space in international legal practice. Most importantly, it puts the social actors of the sea back in to the focus, and repopulates this empty field.