The impact of climate change and sea level rise on coastal regions, such as Hong Kong and Singapore, has become increasingly severe. Over the next 100 years, the land area of these coastal regions will drastically shrink due to sea level rise. Additionally, rapid urban development and population growth in these regions further increase the demand for land. One potential and effective solution to address these challenges is the construction of a new system for human habitation in the remote and open seas. In this study, the future marine urban system is categorized into interrelated subsystems, including safety and protection, green ecological environment, self-sustaining energy, self-sustaining nutrition, transportation, and marine industry chains. The safety and protection subsystem, located on the periphery of the marine urban system, includes new protective structures such as eco-friendly wave-absorbing breakwaters to provide a stable and safe marine environment for habitation. The green ecological environment system requires zero carbon and zero waste emissions from marine cities. The self-sustaining energy subsystem consists of offshore clean energy capture facilities (wind, wave, solar, etc.). The self-sustaining nutrition subsystem is primarily achieved through hydroponic food and large-scale offshore aquaculture. The transportation system includes the internal transportation and logistics network of the marine cities, as well as air and bridge connections to the mainland cities. This article elaborates on the engineering concepts for future marine urban habitation, elucidates potential construction approaches for the related technological systems and subsystems, and explores the future planning of marine urban living and industries.