John R. Gillis critiques the landlocked nature of environmental history, highlighting its neglect of oceans, which comprise most of Earth’s surface and are central to its ecosystems. Western cultural perceptions of the sea as alien, timeless, and resistant to human agency have limited its historical and geographical study, unlike Pacific and Asiatic traditions, which view oceans as integral to human history. Gillis calls for rethinking concepts of land, water, and their interactions by incorporating coasts, watersheds, and migratory movements into environmental history, to produce a richer, borderless history that reflects the intertwined nature of land, sea, and humanity.