The ocean is vast, connecting every continent and touching the shores of most countries around the world. It provides food and livelihoods for millions of people and regulates the climate we all depend on. But who decides what happens in the ocean? Does anyone actually own it?
The short answer is no. No single person, country, or organization owns the entire ocean. Instead, different parts of the ocean are governed under different rules. Coastal nations have authority over waters close to shore, while the vast expanse beyond national waters — the high seas — is shared by everyone.
Understanding where these boundaries lie helps explain everything from who can catch fish to the debate over deep-sea mining — and why protecting the ocean often requires countries to work together.
What are Territorial Waters and Exclusive Economic Zones?
International law divides the ocean into different zones.
Under the United Nations Convention on the Law of the Sea (UNCLOS), coastal countries have full authority over the waters extending 12 nautical miles from their shoreline. These are called territorial waters, and countries can generally manage them much like they do land within their borders.
Beyond and adjacent to territorial waters lies an Exclusive Economic Zone (EEZ). An Exclusive Economic Zone is a sea zone extending up to 200 nautical miles from a country’s coastline, where that country has exclusive rights to use and manage natural resources. Although countries don’t own these waters, the exclusive rights associated with an EEZ allow them to control development and use of economically important resources such as fish, oil and gas, and offshore wind energy.
That means coastal nations, through territorial waters and EEZs, are responsible for managing much of the ocean that people interact with every day.
Who owns the High Seas?
Once you go beyond a country’s EEZ, you enter the high seas.
Making up about two-thirds of the ocean, the high seas belong to no one nation. Instead, they are part of the global commons: areas that belong to no single country that must be managed cooperatively.
Ships from every nation can travel through these waters, and countries can fish and conduct scientific research there, subject to international rules.
Because no one country is in charge, protecting the high seas has long been a challenge.
But there has been progress. In January 2026, the High Seas Treaty entered into force, creating the first global framework for protecting marine biodiversity in international waters. The Treaty creates a legal process to establish marine protected areas on the high seas and conduct environmental impact assessments for activities in international waters. It also creates mechanisms for countries to share the resources found in the high seas more equitably.
The Treaty only applies to countries that have ratified it. So far, 93 countries have done so.
Since the high seas cover about two-thirds of the ocean, protecting them effectively will be critical to achieving the global goal of protecting 30% of the ocean by 2030.
What are the challenges with ocean governance?
Managing a shared ocean isn’t simple. International agreements only work when countries agree to participate and follow the rules, and different nations can have competing interests.
The High Seas Treaty is one example of this. With 93 countries having ratified the Treaty so far, this leaves many still not bound by its rules. To unlock the Treaty’s full potential, more countries must join, participate in decision-making, and turn promises into meaningful protections.
Deep-sea mining is another challenge.
Under UNCLOS, the International Seabed Authority oversees mining in international waters. Countries can decide whether to allow deep-sea mining within their own EEZs, but they need the ISA’s approval to do so on the high seas. To date, no commercial mining has been approved by the ISA in international waters, though the agency has granted exploration permits for companies and countries to study and assess potential seabed mineral deposits.
The United States has never ratified UNCLOS, although it has generally followed many of its principles in practice. Recently, however, the Trump administration announced plans to pursue deep-sea mining in international waters. That move has raised concerns among many countries because it challenges the international system that most nations have agreed to follow.
The debate highlights a broader question: how do we protect a shared ocean when not every country plays by the same rules?
Why does ocean protection matter?
The ocean doesn’t stop at national borders. Fish migrate between countries. Pollution travels on currents. And healthy marine ecosystems help regulate the global climate.
That means decisions made by one country can affect people and wildlife around the world. Effective ocean conservation depends not only on protecting and managing waters within national borders, but also on international cooperation to safeguard the high seas.
How can you help protect the ocean?
Oceana has already helped protect more than 4 million square miles (10 million square kilometers) of ocean habitat by securing marine protected areas, no-take zones, and restrictions on destructive fishing practices such as bottom trawling.
Oceana is campaigning to prevent deep-sea mining while advocating for stronger protections for marine ecosystems around the world.
Learn more about Oceana’s campaigns to protect the ocean and take action today by signing Oceana’s petition to save our oceans from deep-sea mining.
