Although the ocean is investigated by many scientific fields, research about ocean space is scarce. But energy production, extraction of resources, infrastructural and logistical development is increasing incrementally, resulting in a quantum shift in scale and intensity of spatial demands. Almost no part of the global ocean remains unaffected by human impact. The ocean is therefore a site of spatial and environmental convergence, a type of “hinterland” to urbanized territories. While these developments are ephemeral in relative urban terms, often remote and hard to decipher, they also carve out vast territories and leave lasting physical legacies. These phenomena have largely escaped spatial articulation. History is rich in examples of radical forms of urbanization which engaged the ocean as a network agent, without claiming territorial rights. Intensified activities, however have led to the territorialization of the ocean through the establishment of fixed exclusive economic zones. A fundamental contradiction between open ocean systems and bounded space becomes apparent. As opposed to to a territory defined by political borders, this thesis proposes an integrated, kinetic definition of ocean territory based on oceanography and biological thresholds with which urbanizing forces interact. Both the ocean’s inherent spatial properties and cultural interventions become active components. Based on this definition, the first objective is to identify and define specific forms of urbanization within ocean space. Extended urbanization refers to one of the three interacting moments of urbanization proposed by Brenner and Schmid as part of their developing theory on planetary urbanization. This has its conceptual roots in the dual urban processes implosion-explosion as described by Lefebvre in The Urban Revolution. As a specific form of extended urbanization, I argue that ocean space participates in the loose, uneven, and indistinct morphologies we are only beginning to recognize as “urban”. Ocean urbanization is researched first through literature pertaining to four topics which permeate interactions with ocean space and which each represent a rich field of urban theory; Networks, Seascape, Technology and Ecology. Empirical research is then carried out on two case studies; the Barents and the Baltic Seas. These seas undergo a spatial analysis based on the proposed definition of ocean territory. Under urbanization processes, networks lace the ocean floor, the seascape produces energy, technology monitors ecosystems and ecology embraces petroleum exploration. The study distills properties common to both seas, but also distinct manifestations of urban processes within each context. As a result, nine principles of urbanization can be identified. The seas also revealed dispersed intensities in particular locations. Five such situations were chosen as the object of a closer study, which are then proposed as typological conditions: Interpenetration Contraction, Expansion, Assemblage and Confluence. The second objective of the thesis is to relate these findings to current Marine Spatial Planning. What can architects contribute to the conceptualizing, mapping and managing of ocean space? A critical appraisal of ocean planning practice in relation to the research findings, concludes that the architectural challenge is to redraw limits according to ocean dynamics and to launch the ocean project.