This thesis builds on the proposition that the ocean is both an urban and social space. Therefore, marine planning needs to consider socio-cultural risks and opportunities to be deemed sustainable. This reconceptualisation is especially relevant for the Barents Sea, where retreating sea ice leaves the ocean more accessible to marine traffic and resource extraction every year. However, the current practice of marine spatial planning (MSP) responds predominantly to geopolitical and economic demands for resources like gas and oil - only the monetary value of the ocean is considered. It fails to provide an understanding of the ocean as a space of cultural values, memory, and meaning. As a result, the socio-cultural impacts of offshore development remain alarmingly unmapped and unknown. As an interplay between research and design, urbanism can understand human-sea relations and employ this understanding in spatial interventions, where MSP cannot. Following this hypothesis, I aim to approach the Barents Sea as an urban and local project. What does it mean to be at sea, to be changed by the sea, and to change it in return? How is the local economy of life dependent on conditions of marine space? And how can urban designers use this knowledge to affect change. In the first place, this is a theoretical work. I hypothesize what offshore urbanism should entail, propose entrances of design, and compose design principles in the Barents Sea. The theory is tested in a case study: the coastal community of Hammerfest. The current network composition of the Hammerfest maritory shows a system that is overdependent on petroleum activity. The project proposes two pathways of change towards a future where Hammerfest depends on a variety of alternative marine industries. As such, the community becomes more resilient to changes in offshore petroleum. Particularly after 2035, when the current production fields are depleted and extraction moves seaward, away from Hammerfest. Network analysis forms a key point of entrance for the maritorial design. The project regards ships as islands that are inhabited, occupied, and built by humans. They are urban nodes at sea. The maritory can thus be read as an interdependent network of nodes (islands, platforms, pipelines, ships) connected by the movement of goods and people. I use marine traffic density data to analyze the nodal patterns of movement. From it, we can read the organization of marine uses and their spatial relation to Hammerfest. I then select one node from the current network, the island Melkøya, to redevelop as the root of the proposed transition. The prospected departure of the gas industry established on Melkøya provides an opportunity to repurpose the island. Through the act of deconstruction and rehabilitation, the gas processing island is repurposed as a public port, harbouring local marine industry and recreation. From the island Melkøya, a new economy of life is allowed to grow seawards. Ultimately, the purpose of this research is to actuate academics and urbanists to use design as a means to inform and inspire MSP, and to open the discourse on offshore urbanism.