Who owns the sea? Maritime zones and rules

Who owns the sea? No country owns all of it, but each coastal country controls some of it. International law divides the sea into maritime zones, measured outwards from a line along the coast called the baseline (Fig. 1.20). Distances at sea are measured in nautical miles: one nautical mile is 1,852 metres (roughly 6,076 feet), and it matches one minute of latitude, which makes it handy for sea charts.

Walk outwards from the coast:

• Territorial sea (up to 12 nautical miles). The country has near-complete control, just like on land: it makes laws on customs, immigration and pollution. Think of the yard in front of your house: it is really yours, but you must still let a neighbour walk along the path. Here, that 'path' is innocent passage.
• Contiguous zone (up to 24 nautical miles). Limited control, only over customs, tax (fiscal) matters and illegal immigration.
• Exclusive Economic Zone, EEZ (up to 200 nautical miles), set by UNCLOS, the UN's agreement on the law of the sea. The country has special rights to the resources: fish, oil and gas. But it does not own the water: other countries' ships may pass peacefully.
• High seas, beyond everyone's EEZ: international waters, about 64% of the world's oceans. Think of it like this: of every 100 litres of sea, 64 belong to no country. They are a global commons: every country has equal rights to sail, fish, fly over, lay undersea cables, build lawful structures and explore for minerals.

Innocent passage. A foreign ship may pass through a country's territorial sea if it does not threaten that country's peace, good order or security. It must keep moving and not stop, except in an emergency or breakdown. It may not fish or carry out military or other non-peaceful activities.

Problems on the high seas. Because no one country is in charge, there is overfishing, illegal fishing and fights over resources, which hurt the millions who depend on the sea. Out there, a ship follows the laws of its flag state: the country where it is registered.

Rules of the road at sea. Countries follow maritime law so the sea stays safe, fair and peaceful: rules on how ships move, protecting the sea, piracy, terrorism, accidents and disasters, keeping trade routes safe, and settling disputes between countries.

• COLREGs (rules for preventing collisions at sea) are like traffic rules on the road: keep a proper lookout, know which side to pass on, know which ship must give way and which stands on, go at a safe speed, and use lights, sound signals and shapes. Ships also talk by radio and international signals.
• MARPOL is the international agreement to cut pollution from ships.

Without such rules the oceans would be dangerous and chaotic: more pollution, accidents, collisions and fights over resources. With the same rules for every ship from every country, the sea stays safe and clean, and open to every country's ships.