The chapter investigates the conflict between emerging “schools” of environmental thought in the 1960s and 1970s, focusing on Buckminster Fuller’s techno-optimist, libertarian environmentalism and its influence on today’s floating city concepts, like the UN-backed project in Busan. It addresses the questions of why and how Buckminster Fuller’s bright green environmentalism—blending ecological design with market-driven innovation—clashed with the technocritical, governmental reform-oriented dark green environmentalism of US officials and public intellectuals. Analyzing three cases, the chapter argues that these conflicts with dark green environmentalists demonstrated a lack of social acceptance for floating urban structures in US society due to Fuller’s libertarian views, aesthetic issues, pollution concerns, and limited governmental control over oceanic space. The chapter also highlights the lasting impact of Fuller’s ideas through the Whole Earth network and countercultural movements. The chapter contends that governmental and intergovernmental support for floating settlement ideas has grown since the 2010s, shaped by reemerging bright green environmentalist ideas.