Ecological and political instability have time and again emerged as catalysts for risky development projects along India’s southwest coastline. Devika Shankar probes this complicated relationship between crisis and development through a focus on a port development project executed in Cochin in the first quarter of the twentieth century amidst significant political and ecological uncertainty. While ecological concerns were triggered by increasing coastal erosion, a political crisis was precipitated by a neighbouring princely state’s unprecedented attempt to extend its sovereignty over the British port. This integrative environmental, legal and political history brings together the history of British India and the princely states to show how these anxieties ultimately paved the way for an ambitious port development project in the final years of colonial rule. In the process, it deepens our understanding of environmental transformations and development in modern South Asia and the uneven nature of colonial sovereignty.