The Floating City Is Real: Oceanix Busan and the $627 Million Bet on Aquatic Real Estate

A $627 million prototype floating city backed by the UN, designed by Bjarke Ingels Group, and anchored in Busan's harbor may be the most significant bet in real estate history.

Landlord Ledger Publications • Market • 2026-05-04

The idea of building a city on the ocean has existed for over a century, cycling between utopian fantasy and punchline depending on who was pitching it and who was paying for it. In 2025, it is no longer either. At the northern port of Busan, South Korea, the world is preparing to watch the first genuine attempt to float a living, functioning city on the ocean surface: a 15.5-acre cluster of interlocked platforms, backed by the United Nations, designed by one of architecture's most celebrated firms, built by one of the world's largest construction companies, and priced at $627 million. If it works, it does not just demonstrate a technology. It creates a category.

The Origins of an Impossible Idea

Marc Collins Chen did not set out to build the future of real estate. In 2007, the serial entrepreneur was recruited from the private sector to serve as Minister of Tourism for his native French Polynesia, a chain of 118 islands scattered across the South Pacific. His first assignment was mundane: assess whether sea level rise was a threat to the territory. The answer was not. One-third of all French Polynesian islands, he quickly learned, faced submersion by 2035 or 2050, depending on which projections you trusted. That was not a policy problem. It was an extinction-level event for entire communities.

Collins Chen spent the next decade trying to solve it. He connected French Polynesia with the Seasteading Institute to explore floating infrastructure, co-founded the Blue Frontiers company to develop what became known as the Floating Island Project, and watched it collapse in 2018 under mounting opposition from locals who saw it as a tax-free playground for the wealthy. What he brought out of the wreckage was a lesson: floating cities could not be sold as libertarian experiments or luxury escapes. They had to be built for everyone, anchored to real governments, and justified by climate math, not philosophical aspiration.

In 2017, Collins Chen met Itai Madamombe, a former senior advisor to UN Secretary-General Ban Ki-moon who had spent years building multi-stakeholder partnerships across global development. She had reached the same conclusion from a different direction: floating communities were not just an engineering question, they were the right vehicle for complex problem-solving at civilizational scale. Collins Chen relocated from Tahiti to New York City. Madamombe left the UN. Together, they founded OCEANIX in 2018.

The Deal That Made It Real

For two years, OCEANIX operated as a concept company with compelling renderings and a persuasive climate argument but no ground to build on. That changed in April 2019, when UN-Habitat co-convened the first-ever UN roundtable on sustainable floating cities, where OCEANIX unveiled its vision to an audience of government ministers, mayors, and high-ranking UN officials. The scale model of the proposed city later went on display at the Smithsonian Museum's FUTURES exhibition. The concept had arrived in the right room.

In November 2021, on the heels of COP26, the Busan Metropolitan City, UN-Habitat, and OCEANIX signed a formal agreement to build the world's first prototype sustainable floating city in Busan's active harbor. The site was not accidental. Busan, South Korea's second largest city with 3.4 million residents, is home to the fifth-largest container port in the world, with deep water, gentle tides, and a local engineering ecosystem built around major maritime construction. One district in Busan already faces submersion as early as 2030. The city had both the incentive and the infrastructure to say yes.

In April 2022, at the Second UN Roundtable on Sustainable Floating Cities at UN headquarters in New York, OCEANIX unveiled the full design. The project's cost came into focus: $10,000 per square meter across 15.5 acres, totaling approximately $627 million. The platforms would be assembled on land and towed to the harbor, a construction method that reduces cost and complexity. OCEANIX CEO Philipp Hofmann announced the team was on track to deliver.

What They Are Actually Building

Oceanix Busan is not a single structure. It is an interconnected system of three platforms, each purpose-built, totaling 6.3 hectares, designed to house 12,000 people in its initial phase, half residents and half visitors, and eventually expandable to over 20 platforms accommodating more than 100,000.

The lodging platform covers 30,000 square meters and includes harbor-view accommodation, organic dining, and skylit greenhouse amenities. The research platform, at 37,000 square meters, functions as a co-working and maritime research hub anchored around a shared winter garden with hydroponic towers. The residential platform, at 34,000 square meters, combines low-rise housing with local cultural programming and a communal backyard at its heart.

The architecture was led by Bjarke Ingels Group, the Copenhagen and New York-based firm behind some of the most discussed buildings of the past two decades, working alongside Seoul-based SAMOO Architects and Engineers, part of the Samsung Group. The engineering team includes Arup, Transsolar KlimaEngineering, Sherwood Design Engineers, and artist Olafur Eliasson's Studio Other Spaces, which contributed the design of public spaces. Construction expertise comes from Bouygues Construction, one of France's largest building conglomerates.

The platforms are coated in Biorock, a material invented by architect and marine scientist Wolf Hilbertz in 1976. Biorock is formed when a low-voltage electric current passes between underwater metal electrodes in seawater, causing dissolved minerals to accrete onto a cathode and form a thick layer of limestone. The material is described as the only marine construction substance that grows stronger with age and self-repairs when damaged, continuously reinforced by the surrounding seawater as long as the current flows. Its use does not merely protect the platforms from corrosion; it actively regenerates marine habitat, building artificial reef structures that support coral, fish, and aquatic biodiversity beneath each platform.

Six integrated systems run through every platform: zero-waste and circular systems, closed-loop water management, on-site food production, net-zero energy generation, innovative mobility, and coastal habitat regeneration. Energy comes entirely from floating and rooftop photovoltaic panels, micro wind turbines, and battery storage. Water is harvested from rain, desalinated from the sea, and recycled in closed loops. Food is grown through aquaponics and vertical farms integrated into each platform, with oysters filtering up to 50 gallons of ocean water per day and kelp absorbing carbon at five times the rate of land-based plants. There are no cars. There are no fossil fuels. Adjustable ballast systems allow the entire structure to rise with sea levels rather than resist them.

The platforms connect to Busan's port via link-span bridges that frame what OCEANIX calls its Blue Lagoon, a sheltered body of water serving as a site for floating recreation, art installations, and performance spaces.

The Material That Makes It Possible

The specific chemistry of Biorock deserves more attention than it typically receives. When steel is electrified in seawater, something counterintuitive happens: instead of corroding, it un-corrodes. Red rust turns grey and black, converting back to iron. Then white limestone minerals that are naturally dissolved in seawater begin to grow over the surface, producing a constantly thickening layer of hard rock that becomes denser the longer the process continues. The Global Coral Reef Alliance, one of Oceanix's partners, has built approximately 500 Biorock reef structures in over 20 countries. The technology has been proven at reef scale. What Oceanix is betting on is whether it can perform at city scale.

Co-founder Itai Madamombe described the logic this way: the structure does not fight the ocean. It recruits the ocean. The seawater is not an adversary to be repelled; it is a supplier of raw materials, continuously delivering minerals to strengthen the very walls of the city submerged within it. It is, in the most literal sense, a building material that the ocean provides continuously and for free.

A Real Estate Category That Does Not Exist Yet

The market argument for floating cities has nothing to do with luxury or novelty. It is arithmetic. Two out of five people globally live within 100 kilometers of a coastline. Ninety percent of the world's mega-cities are vulnerable to rising sea levels. The standard response, managed retreat from the coast, is politically untenable in most of these places. As Collins Chen has put it, using the example of French Polynesia: people do not want to leave the places where they buried their ancestors. The ocean is not a threat to be fled. For many communities, it is home.

Conventional coastal adaptation strategies, seawalls, flood barriers, elevated foundations, buy-out-and-move programs, all share a structural limitation: they fight geography rather than reimagining it. They assume that land is fixed and that the problem is water encroachment. Oceanix inverts the premise. If the platform rises with the water, sea level rise is no longer a threat; it is simply irrelevant.

The real estate implication is significant. Land, particularly coastal land, is finite. Oceanix platforms are modular, manufacturable off-site, towable to any coastal harbor in the world, and theoretically unlimited in number. At $10,000 per square meter, the Busan prototype is priced comparably to high-end urban real estate in major coastal markets, not as subsidized housing. But Oceanix has been explicit that affordability is a design goal, not an afterthought. Because no land is purchased, because platforms are built off-site with industrial efficiency, and because some governments have signaled interest in subsidizing floating affordable housing, the economics are not fixed. They are negotiable in ways that land-based real estate never is.

OCEANIX has disclosed that it is in active discussions with at least ten other governments about building floating cities. If the Busan prototype performs as designed, that number will grow. Each successful prototype is not just a building. It is a regulatory and engineering proof-of-concept that removes a layer of resistance from every subsequent conversation.

The Skeptics Are Not Wrong

The history of floating city proposals is long and mostly unbuilt. R. Buckminster Fuller's Triton City in the 1960s, Kenzo Tange's Tokyo Bay Plan, the Seasteading Institute's various iterations: all generated serious architectural attention and produced nothing at scale. The pattern is recognizable: compelling renderings, serious funders, early enthusiasm, then reality.

Critics of Oceanix Busan point to several structural concerns. The technology involved in self-sustaining aquaponics, closed-loop water systems, and on-site energy generation has not been simultaneously integrated and operated at city scale. Maintaining a closed-loop system in a marine environment exposed to salt corrosion, storms, and biological fouling is categorically different from doing so in a controlled lab. The regulatory environment for floating cities remains fragmented globally; permitting a structure that is neither a vessel nor a building crosses jurisdictions in ways that can stall or kill projects. And there is the deeper social question, first raised loudly in French Polynesia: who actually gets to live there?

Madamombe addressed the last question directly in describing the initial community composition: a cross-section of Busan's population, focused specifically on blue-tech innovators and maritime researchers working on climate and habitat problems. This is a community justified by function, not income. Whether that logic holds as the project scales is an open question the Busan prototype cannot answer until it exists.

The timeline has already slipped. Original targets called for construction to begin in 2023 and complete by 2025. As of 2026, the project continues to move through permitting, regulatory approvals, and engineering finalization. UN-Habitat and Oceanix reaffirmed in 2023 a commitment to begin construction by 2025, targeting the first housing module by 2028. Whether that schedule holds is now the central question.

The Bet

What distinguishes Oceanix Busan from its predecessors is the quality of its institutional backing. The Seasteading Institute had Peter Thiel's money and libertarian ideology. Oceanix has UN-Habitat's policy infrastructure, Bouygues Construction's engineering track record, Bjarke Ingels Group's design credibility, and the sovereign endorsement of South Korea's second-largest city. These are not decorative endorsements. They are the difference between a manifesto and a building permit.

Collins Chen has described his vision not in terms of architecture or engineering but in terms of land. He is not building a prototype. He is building the proof that ocean surface can become real estate, that sovereign-adjacent, modular, scalable development is not science fiction but the next frontier of urban expansion. If the Busan platforms rise in their harbor and perform as designed, the $627 million will be remembered not as the cost of a building but as the seed investment for an entirely new asset class. There is no precedent for what comes next. That is the point.