In the previous installments of “The Theory of Marine Civilization,” we have been exploring why humanity needs a new civilization and why the ocean serves as its stage. However, a civilization cannot be built on ideals alone. No matter how excellent a vision may be, it is impossible to build a sustainable society without the infrastructure to support it.

In this second series, we will reexamine the foundations of civilization from the perspective of “water.” Water is not merely a resource. It is the “real infrastructure” that supports all aspects of society—from drinking water and food production to energy, logistics, disaster prevention, sanitation, and industrial activities.

To realize a maritime civilization, we must first understand water. This is because a maritime civilization is one that coexists with water and is built upon the water cycle.

■Civilization Has Developed Alongside Water

Looking back at human history, civilization has always developed alongside water.

The Nile, the Tigris and Euphrates, the Indus, and the Yellow River—the world’s four great civilizations have all benefited from abundant water resources; by harnessing water, they have developed agriculture, sustained people’s livelihoods, and shaped their societies.

Japan, too, is blessed with abundant rainfall and numerous rivers, and has fostered its own unique culture and industries through paddy-field agriculture and water transportation.

As you can see, water is not merely a resource for daily life.

It connects people, transports goods, nurtures food, generates energy, and supports economic activity—it has served as the very foundation upon which civilization itself is built. However, while past civilizations have excelled at “utilizing” water, they have not fully incorporated the “cycle” of water itself as a fundamental pillar of civilization.

With population growth, urbanization, and industrial development, water has come to be treated as a “resource to be used,” while its natural cycle and harmony with nature have gradually been lost.

What is needed in the coming era is not a civilization that treats water merely as a resource, but one that redesigns society itself based on the water cycle and coexistence with nature.

The marine civilization we advocate aims to embody precisely that new form of civilization.

■The Limits of Fixed Infrastructure Civilizations

Modern society has been built upon a vast network of fixed infrastructure, including dams, water supply and sewage systems, power plants, roads, ports, and communication networks. These systems have greatly enhanced urban development and the convenience of daily life, serving as a vital foundation that supports modern society.

However, fixed infrastructure is based on one major assumption: that society will continue to function stably in the same location. Yet today, natural disasters such as earthquakes, tsunamis, torrential rains, typhoons, and droughts are becoming increasingly severe, and rising maintenance costs due to population decline and aging infrastructure have also become serious challenges. Once infrastructure is damaged, urban functions—including water supply, electricity, logistics, and communications—come to a cascading halt, significantly impacting people’s lives and local economies.

What we are facing is not merely the aging of facilities. Amid major changes in the natural environment and social structures, we are confronting the limitations of the civilizational system itself—a system that continues to rely on fixed structures.

What is needed going forward is not a rejection of fixed infrastructure, but a new way of thinking that does not rely solely on it. We must transition to a flexible civilizational system capable of relocating, decentralizing, and circulating necessary functions in response to changing natural environments and social conditions.

■A New Concept: The Water-Cycle Civilization

Water in nature never remains in one place. Water that evaporates from the ocean forms clouds, falls as rain on the mountains, flows as rivers to nourish the land, and eventually returns to the ocean. This ceaseless cycle nurtures life, sustains ecosystems, and maintains the balance of the Earth’s environment.

Nature is sustained by this “cycle.” Future civilizations, too, must learn from this natural mechanism.

The “Water Cycle-Based Civilization” we advocate is not merely a society that recycles water resources. It is a society that makes the water cycle the very foundation of civilization itself. It is a society in which, with water as the starting point, energy, food, resources, information, and human talent are interconnected and develop sustainably through a cycle of circulation. In such a society, humans do not dominate nature but coexist as part of its cycle. This is the fundamental philosophy of a water-cycle-based civilization.

Civilizations to date have built their prosperity through one-way development characterized by mass production, mass consumption, and mass disposal. However, what is needed in the coming era is a civilization in which people, society, and the environment can all sustain themselves in harmony with nature’s cycles.

A water-cycle-based civilization is neither merely an environmental measure nor the development of new infrastructure. It is a new model of civilization that incorporates nature’s cycles into the fabric of society and redesigns civilization itself, grounded in the restoration of humanity and coexistence with nature.

■The Future Seatopia Aims For

Project Seatopia is an initiative designed to demonstrate the marine civilization we advocate for in the real world.

A marine civilization cannot be realized through ideals alone. It requires a system in which the social functions that support people’s lives—such as water, energy, food, resources, information, healthcare, and communications—work in tandem and circulate sustainably in harmony with nature.

Seatopia is a demonstration platform designed to bring this new civilizational system to life. By utilizing renewable energy, recycling water resources, making efficient use of resources, and incorporating self-sufficient social functions, Seatopia serves as a hub for research, education, international exchange, and technological demonstration—a model for future society—during peacetime. In the event of a disaster, it functions as a “Mobile Emergency Relief System,” moving its entire operational infrastructure to the affected area to rapidly provide essential services such as water, electricity, communications, and medical care, thereby supporting people’s lives.

Seatopia is not merely a ship. Nor is it a floating city. It is a mobile platform that demonstrates a maritime civilization by integrating social functions—including the water cycle—based on coexistence with nature.

■Marine Civilization Begins with Water

A marine civilization is not simply about building cities on the sea. It is about creating a new civilization—one in which people and nature coexist and develop sustainably, with the sea as the stage and the water cycle as the foundation. To achieve this, it is essential to rethink water not merely as a resource, but as the foundation that nurtures life, supports society, and enables civilization itself.

Water is not merely a source of drinking water or irrigation; it is the “foundational infrastructure of civilization” that supports all social activities—including energy, logistics, food, disaster prevention, industry, and the environment. That is precisely why the first step toward understanding a marine civilization lies in understanding water.

The ocean is the center of the Earth’s water cycle and the source that nurtures life and civilization. The maritime civilization we aim to build seeks to incorporate this water cycle into the fabric of society and realize a new civilization where people and nature coexist.

Marine civilization is a civilization built on the ocean as its stage and the water cycle as its foundation. Therefore, contemplating the future of marine civilization is also contemplating the future of water. And the first step toward that future begins with reexamining the question, “What is water？”