Increasing use of the marine environment makes the development of spatial planning desirable. However, ambiguity and connectivity in the marine system has the potential to create conflict between neighboring States, particularly in contested border regions with overlapping ecosystems and migratory species. Interest in the concept of transboundary conservation is expanding in the marine system. Increasingly, there is a strategic move toward attempting to combine conservation issues with resolving conflicts between States by promoting these initiatives as peace parks. Although this strategy has the potential to provide solutions there are risks involved. A review of nine marine transboundary initiatives provides insights into hazards and best practices that may inform future conservation and spatial planning in this system. Results suggest that, like most conservation, long-term sustainability of projects is based on transparency, the availability of appropriate funding, and governmental will. While the branding of marine transboundary conservation initiatives as peace parks may help to provide initial political impetus to projects, maintaining governmental interest is a significant long-term issue. This review aims to stimulate the debate on strategies for developing marine transboundary conservation for the future, bearing in mind the potential for conflict in these regions.