Land can be divided up somewhat clearly (although there are disputes about who owns what), but what happens when it comes to water? Technically, no one owns the ocean, but some countries have jurisdiction in some seas.
According to a UN law, coastal countries or states with archipelagos have sovereignty over their territorial seas, which means waters up to 12 nautical miles (22km) from their shores, including the air above and the seabed below. However, this can be shorter if two states are closer together.
In the UK, the Crown claims ownership of nearly all waters within 12 nautical miles. People who want to use these waters for ports, windfarms or aquaculture projects must apply for a lease.
Landlocked countries don’t have territorial waters, but vessels can access the seas for ‘innocent passage’. If they’re not doing things such as spying, using weapons or fishing, then they are allowed to pass through freely.
Beyond that, coastal countries have Exclusive Economic Zones (EEZs) within 200 nautical miles (370km) – or less, if zones of different nations would overlap. Because of its overseas territories, including Guadeloupe, Réunion and French Polynesia, France has the world’s largest EEZ.
Countries don’t have as much control of their EEZs as they do over their territorial seas, but they can fish, drill for oil, lay undersea cables or even build artificial islands. They are also responsible for conservation measures and fishing quotas. Other countries can fish in that EEZ, as long as they follow any rules set out.
What are the High Seas?
Travel further and you reach the High Seas. These international waters are outside the jurisdiction of any nation and make up two thirds of the ocean. Anyone can use the High Seas for travel, fishing or research, if they follow international laws.
Just 1.2 per cent of international waters are protected but conservationists are hoping to change this. In 2023, members of the UN agreed to adopt the High Seas Treaty, which aims for better protections. In September 2025, 60 countries, including the UK, had signed the Treaty – meaning the agreement will now become law.
The ocean is full of fascinating marine species, from tiny plankton to the enormous blue whale. While they’re swimming freely, humans can’t own these animals, and migratory species such as whales and turtles aren’t aware of any boundaries set by humans. Yet, more than one trillion wild fish are caught each year. If someone catches a fish legally, they are generally considered the owner.
Top image credit: Getty