Exclusive Economic Zones — Who Owns the Ocean, and What Belongs to No One

An Exclusive Economic Zone is the belt of sea, extending up to 200 nautical miles (about 370 km) out from a country's coast, in which that country has the exclusive right to explore and use marine resources — fishing, oil and gas, seabed minerals, wind farms — and to control activities like laying cables and pipelines. It was established by the UN Convention on the Law of the Sea (UNCLOS), agreed in 1982 and in force since 1994. An EEZ is not the same as full sovereignty: other nations keep the freedom to sail and fly through it and to lay their own cables. Closer in, a narrower 12-nautical-mile territorial sea is treated almost like the country's own land (UNCLOS, 1982).

France — and it surprises people, because France isn't usually thought of as a sea power. Through its overseas territories scattered across every ocean (French Polynesia alone is nearly 5 million km²), France's EEZ totals over 10 million km², which is either the largest or the second-largest on Earth depending on how it's measured. The United States is the other contender at about 11.35 million km², spread across three oceans plus the Gulf of Mexico and the Caribbean. Different bodies (Sea Around Us, Marine Regions, the Pew Research Center) calculate these areas slightly differently, and France and the US trade the top spot by method — so the honest answer is that they are the two giants, neck and neck (Sea Around Us; Wikipedia; Marine Insight, 2024–2025).

Because an EEZ is measured from a coast — and even a tiny, uninhabited island generates a 200-nautical-mile zone all around it. A nation with a handful of far-flung islands can therefore claim an enormous area of sea. France is the clearest case: French Polynesia, New Caledonia and other scattered territories give it the world's biggest ocean estate from a country that is just 0.45% of Earth's land. New Zealand sits on a mostly-submerged continent and has an EEZ around fifteen times its land area. The UK's modest home waters are dwarfed by the zones around Ascension, the Falklands and other overseas territories. It's why some disputes over bare rocks are really disputes over the vast ocean they would unlock (UNCLOS, 1982; Sea Around Us, 2024).

After France and the US, the biggest are Australia (~8–9 million km², roughly matching its land), Russia (~7.6 million km², along its long Arctic and Pacific coasts), and the United Kingdom (~6.8 million km², the world's fifth-largest, almost all from overseas territories). Japan has about 4.47 million km² from its thousands of islands, and New Zealand about 4 million km². Each of these is enormous relative to what you'd guess from a land map — a reminder that ocean area and land area are two very different rankings (Sea Around Us; Marine Insight; WorldAtlas, 2024–2025).

The high seas are everything beyond every country's EEZ — the open ocean that belongs to no nation. They cover about 64% of the ocean's surface, which is roughly 43% of the entire planet, making them the largest unowned space on Earth. Under UNCLOS they are a 'global commons,' open to all states for navigation, fishing and research, and the deep seabed beneath them — 'the Area' — is declared the 'common heritage of mankind,' which no state may claim. Long imagined as a barren desert, the high seas are now known to hold much of the ocean's biodiversity and most of its volume (Pew; NOAA; IUCN, 2014–2024).

Not quite — but they have been dangerously under-governed. Ships, crews and companies on the high seas are still bound by international law and by the flag state whose flag a vessel flies, and bodies like regional fisheries organisations and the International Seabed Authority oversee particular activities. But there was no overall framework to create marine reserves or protect biodiversity out there — which is why, after nearly two decades of talks, UN members agreed a High Seas Treaty (the BBNJ agreement) in 2023, allowing protected areas to be established in the open ocean for the first time. It comes into force once enough nations ratify it (UN High Seas Treaty, 2023).

China claims almost the entire South China Sea inside a 'nine-dash line' drawn on a 1947 map — overlapping the EEZs of the Philippines, Vietnam, Malaysia, Brunei and others, in a sea that carries over $5 trillion of trade a year and is rich in fish and energy. In 2016 an international tribunal at the Permanent Court of Arbitration in The Hague, ruling on a case brought by the Philippines, found that China's claim to historic rights inside the line had no legal basis under UNCLOS. China rejected the ruling and continues to assert the claim, which is why it remains the world's tensest maritime dispute (Permanent Court of Arbitration, Philippines v. China, 12 July 2016).

Because the ice that long made it unreachable is melting, opening newly accessible oil, gas, fishing grounds and shipping routes. Russia, Canada, Denmark (through Greenland), Norway and the United States are all working to extend their seabed rights far out under the central Arctic, using the UNCLOS rules that let a country claim the continental shelf beyond 200 nautical miles where it can prove the seabed is a natural extension of its land. Russia even planted a flag on the seabed at the North Pole in 2007. These overlapping submissions to the UN Commission on the Limits of the Continental Shelf are one of the great unsettled questions of who owns the sea (UNCLOS; UN CLCS submissions, 2007–2024).

No — and the layer is honest about that. The dashed arcs drawn here are schematic illustrations, simplified to a handful of points, of roughly where a 200-nautical-mile zone reaches around a few headline island groups (French Polynesia, Hawaii, New Zealand). They are meant to make the 'a tiny island, a huge zone' idea visible, not to show exact borders. Real maritime boundaries are precise legal lines, calculated from baselines and treaties; the authoritative dataset is the Marine Regions (VLIZ) Maritime Boundaries Geodatabase, which is the source for the boundary concept used here. Nothing on this map should be used for navigation or any legal or economic purpose (Marine Regions / VLIZ, CC-BY; UNCLOS).

EEZs are the legal 'why' behind where boats are allowed to work. Switch on the Ocean canvas's Fishing Fleets layer and you'll see real vessel activity — much of which clusters inside national EEZs, where a country controls fishing rights, and thins out (or turns contentious) on the high seas. The maritime-chokepoints overlay shows where that traffic is forced through narrow gates. Together they tell the same story from different angles: who owns the water, where the trade squeezes through, and where the boats actually go.