Subversive Seas begins in late 1926, when strikes in western Java and Sumatra were violently crushed by Dutch police forces. Dutch attitudes blamed the revolts on dangerous foreign influences entering the colony’s shores and assumed suspicious persons were fleeing the colony onboard ships bound for Asian and Middle Eastern ports. The maritime world, therefore, played an important role in subsequent projects ‒ collaboratively executed by Dutch shipping companies and the colonial administration ‒ to extinguish the perceived movement of subversive people and ideas around the globe. The introduction provides a brief overview of Dutch shipping, impacts of the Dutch Ethical Policy, and the rise of Indonesian nationalism, as well as the narrative’s theoretical framework and historiographical interventions. Ultimately, repositioning colonial Indonesia to a subimperial center at the nexus of its own connective maritime webs provides a deeper understanding of how the ocean’s permeable boundaries created a simultaneously liberating and threatening maritime spatiality and exposes the fundamental differences between terrestrial and oceanic characteristics particular to the interwar Dutch Empire.