What Are Maritime Zones Under UNCLOS?

When you look at the ocean, it might seem endless. The sea is a vast blue space with no fences or borders.  But in reality, the sea is carefully divided by invisible lines. Each line represents a country’s rights, responsibilities, and freedoms at sea. These divisions are called maritime zones, and they were established under a global agreement known as the United Nations Convention on the Law of the Sea (UNCLOS).

The rules in UNCLOS tell us who owns what parts of the ocean. From the smallest fishing boat to the largest oil platform, every activity at sea takes place within a framework shaped by UNCLOS. Without it, there would be constant disputes over fishing rights, navigation, and offshore resources. 

In this article, you’ll learn what these maritime zones are, why they matter, and how they shape the way countries use and protect the ocean.

What Is UNCLOS?

Before diving into the maritime zones, it is important to understand what UNCLOS actually is.

The United Nations Convention on the Law of the Sea (UNCLOS) was adopted in 1982 and came into force in 1994. It is a global agreement that sets the rules for how countries use the ocean. Today, more than 160 countries have agreed to follow the guidelines of UNCLOS.

UNCLOS defines how the sea should be used, shared, and protected. It gives clear guidelines about maritime boundaries, navigation rights, environmental protection, and the management of ocean resources. 

Before UNCLOS, there were many conflicts between countries over ocean areas. Some nations claimed large stretches of the sea as their own, while others argued that the ocean should remain free for everyone. 

UNCLOS solved the matter by dividing the ocean into zones with invisible lines. Each zone gives a clear rule about who has control and what activities are allowed. It also covers important topics like environmental protection, freedom of navigation, and the management of seabed resources. 

How Maritime Zones Are Measured

All maritime zones under UNCLOS start from the baseline. It is usually the low-water line along the coast as marked on official charts. From this baseline, distances are measured outward into the sea, in nautical miles (NM).

• 1 nautical mile (NM) = 1.852 kilometers.

Using this system, UNCLOS divides the ocean into several key zones. Each zone gives the coastal state different levels of rights and responsibilities. Let’s explore each of these zones in simple, clear terms.

a. Internal Waters

Internal waters are all waters on the landward side of the baseline. This includes ports, harbors, bays, rivers, and estuaries connected to the sea. 

In simple terms, internal waters are just like land territory. 

A coastal state has complete control over its internal waters. The government can make laws, enforce them, and decide who can enter. Foreign ships need permission to enter these waters.

For example, the Port of Colombo in Sri Lanka and Sydney Harbour in Australia are both within internal waters. The government of each country manages these areas completely.

In short, internal waters are fully national waters.

b. Territorial Sea (Up to 12 Nautical Miles)

The territorial sea extends up to 12 nautical miles from the baseline. Within this zone, the coastal state enjoys full sovereignty. It can enforce laws, regulate resource use, and control the movement of vessels. 

However, ships from other nations are allowed to pass through this area under what is called innocent passage. This means foreign ships can move through as long as they do not threaten the peace, security, or environment of the coastal state.

You can think of the territorial sea as an extension of a nation’s land territory into the ocean, where the country has the same power as it does on land.

Innocent Passage: Foreign ships, including warships, are allowed to pass through a country’s territorial sea as long as their passage is innocent. That means they must not engage in any activities that threaten the peace, security, or order of the coastal state.

c. Contiguous Zone (12 to 24 Nautical Miles)

The contiguous zone begins right after the territorial sea and stretches up to 24 nautical miles from the baseline. 

Here, the coastal state doesn’t have full sovereignty. But it does have the right to enforce specific laws related to customs, immigration, fiscal policies, and pollution control.

This zone allows countries to take preventive measures and punish violations that occur near their coastlines.

For instance, if a ship dumps waste in the territorial sea and escapes a few miles further out, the coastal state can still take action within the contiguous zone.

In other words, the contiguous zone is where a country can take preventive actions to protect its borders and maintain security.

d. Exclusive Economic Zone (EEZ – Up to 200 nautical miles)

The Exclusive Economic Zone (EEZ) is one of the most important maritime zones. It extends up to 200 nautical miles from the baseline. 

Within this zone, the coastal state has special rights to explore, exploit, manage, and conserve the natural resources of the water, seabed, and subsoil.

These resources include fish, oil, gas, and minerals. The country also has the right to generate energy from water, wind, and currents within this area.

However, other countries can still use the EEZ for peaceful navigation, flying over the area, and laying submarine cables and pipelines. This means the EEZ gives economic rights, but not the total ownership.

The EEZ is a great example of balance. It ensures economic benefit for the coastal state while maintaining freedom of the seas for everyone else.

e. Continental Shelf

The continental shelf refers to the seabed and subsoil extending beyond the territorial sea, often up to 200 nautical miles, and sometimes further. It is basically the underwater extension of a country’s landmass.

Think of the continental shelf as the underwater extension of a country’s landmass. A coastal state has the exclusive right to explore and extract non-living resources like oil, gas, and minerals. It can also explore for living organisms attached to the seabed, such as corals or sponges.

What’s interesting is that even if a country doesn’t claim its continental shelf, it still automatically owns the rights under UNCLOS.

f. High Seas

The high seas begin beyond the EEZ. It is outside of a country’s jurisdiction. 

The high seas are free for all nations to use for peaceful purposes such as navigation, fishing, flying, laying submarine cables, and scientific research. Every country shares equal rights and responsibilities here. 

But this freedom also comes with shared duties. Nations must cooperate to protect marine life, prevent illegal fishing, and reduce pollution.

Why Maritime Zones Are Important

Maritime zones are not just lines drawn on a map. They play an important role in maintaining peace, managing resources, and protecting the environment. Let’s see why they matter so much.

• Prevent Conflicts: Before UNCLOS, countries often argued about who owned the sea. These disputes sometimes led to serious conflicts. Maritime zones clearly define boundaries and help reduce misunderstandings. 
• Manage Ocean Resources: The ocean is full of valuable resources. From fish and minerals to oil and gas, all are available at sea. Maritime zones allow countries to manage and protect these resources responsibly within their EEZ and continental shelves.
• Protect the Environment: Maritime zones also support environmental protection. Countries have a duty to keep their waters clean and safe from pollution. They must prevent oil spills, manage waste properly, and protect marine habitats. UNCLOS ensures the ocean remains healthy for future generations.
• Support Global Trade: About 90% of world trade happens by sea. Maritime zones make this possible by defining safe routes for ships and protecting freedom of navigation. Without these zones, shipping routes could easily become disputed, disrupting global commerce.

Final Thought

The ocean connects every part of our planet. Maritime zones are more than just invisible lines on a map. They represent the effort of the global community to share, protect, and respect the world’s oceans.

From the smallest fishing boat to the largest oil platform, every activity at sea takes place within a framework shaped by UNCLOS. Through UNCLOS, countries have found a fair and balanced way to share this vast resource.