Since industrialization, the spaces of oceans and seas have been filled with multiple industrial functions to serve land-side activities and the growth of modern cities. In line with the concept of planetary urbanization (Brenner/Schmidt), Nancy Couling has proposed the concept of urbanization of the sea, captured also in our book by the same name (Couling/Hein 2020). With the discovery of petroleum and its growing use for industrial practices, the sea became a highway for oil transport. Adapting ships for petroleum transportation over time, increasing sizes and forms, started a process of transformation of seas, coasts, and other bodies of seas. The discovery of deep-sea oil and the construction of drilling platforms, the laying of pipelines, further changed the sea spaces. The Ekofisk complex of platforms and structures was created in 1969 some 300 kilometers southeast of Stavanger as a transportation hub for a number of surrounding oil fields and just one example of the extensive installations in the sea. This oil platform is just one example of the diverse activities that have filled the sea over the last five decades. Energy infrastructures in the sea are no longer limited to petroleum; large wind farms are another, more recent, form of occupying the sea. The physical infrastructures for oil or wind, are just one part of the transformation of the sea. They depend on national, EU, and global policies, legal systems, maritime plans, and other “hidden designers” that provide the foundation for spatial interventions. Understanding both the impact of spatial structures and hidden ones is key to rethinking the sea as a space for more than industrial interventions, creative practices, architectural and urban design interventions, social practices, and cultures that capture the richness and complexity of the sea.