Ecosystem-Based Management (EBM) integrates the connections between land, air, water and all living things including human beings and their institutions. The location of the Irish Sea, between major historical industrial centres, its history of use and exploitation, combined with its hydrographic characteristics, have led to the current patterns of use. EBM efforts have been ongoing for over a decade but political boundaries have led to fragmented governance. The forthcoming UK exit from the European Union (EU) may pose further challenges. This chapter examines articulations between political boundaries, spatial scales of Marine Spatial Planning and nested social-ecological systems including the gyre in the western Irish Sea, and Dublin Bay. Examples of emerging best practices are provided and the challenges of data availability for ecosystem services are considered.