Ocean-based development strategies are widely promoted as engines of sustainable growth capable of simultaneously delivering environmental protection, economic expansion, and social inclusion. However, emerging evidence suggests that these initiatives often produce uneven distributive outcomes across coastal regions. This article investigates how institutional configurations within ocean-based development projects influence the distribution of economic benefits and livelihood risks among coastal communities. Using a comparative dataset of sixteen marine development initiatives across Africa and Southeast Asia, including fisheries modernization programs, coastal tourism zones, and marine spatial planning projects, the study evaluates how governance structure, capital intensity, and participation mechanisms affect income retention and resource access. The findings demonstrate that capital-intensive, investor-driven projects systematically correlate with reduced local income retention and higher livelihood displacement risk, whereas participatory governance arrangements mitigate distributive inequality. The study concludes that marginalization in ocean development is driven less by ecological constraints than by institutional design choices, underscoring the importance of governance reforms that prioritize tenure security, participatory authority, and revenue redistribution.