US submarine sinks Iranian warship IRIS Dena off Sri Lanka for first time since World War II

The developments have brought renewed focus to the legal zones dividing the world’s oceans, territorial waters, exclusive economic zones and international waters.

According to the United Nations Convention on the Law of the Sea (UNCLOS), a country’s territorial waters extend up to 12 nautical miles from its coast.

Within this area:

• The coastal state exercises full sovereignty, similar to its land territory.
• It can regulate security, fishing, navigation and military activity.
• Foreign ships can only pass under the principle of “innocent passage.”

If a military attack occurs in territorial waters, it is usually considered a direct violation of sovereignty, which can intensify diplomatic or military tensions.

What is the Exclusive Economic Zone (EEZ)?

Beyond the territorial waters is the Exclusive Economic Zone or EEZ, which extends up to 200 nautical miles from the coast.

In an EEZ:

• The coastal state has exclusive rights to natural resources, including oil, gas and fisheries.
• However, the waters themselves remain open to navigation by other countries.
• Foreign ships can sail, but resource extraction requires permission.

The Sri Lankan government said the second Iranian ship currently being monitored is located within its EEZ but outside the country’s maritime boundaries, meaning Colombo has economic rights there but not full control over shipping.

“A U.S. submarine sank an Iranian warship that it thought was safe in international waters,” U.S. Defense Secretary Pete Hegseth said at the Pentagon. “Instead, she was sunk by a torpedo. Quiet death.”

A Pentagon video that reportedly captured the attack showed a large explosion that shattered the rear of the ship, lifting it out of the water and causing it to begin sinking from the stern.

What are international waters?

The waters beyond 200 nautical miles from the coast of any country are known as international waters or the high seas.

These areas:

• Don’t belong to any country.
• They are open to navigation, overflights and maritime operations by all states.
• Vessels are governed by the “law of the flag”, which means that they are under the jurisdiction of the country where they are registered.

Navies of different countries regularly operate in international waters, particularly for patrols, exercises and strategic deployments.

Why maritime zones are important in the war between Iran and the United States

Incident details: A United States Navy submarine torpedoed the IRIS Dena using a Mark 48 heavy torpedo. This is the first time a U.S. submarine has sunk an enemy surface ship with a torpedo since World War II.

Location: The sinking occurred approximately 40 nautical miles (74 km) off the coast of Galle, Sri Lanka.

The sinking of the IRIS Dena, which had reportedly participated in a naval exercise organized by India in the Bay of Bengal before returning, has raised concerns about the expansion of the confrontation between the United States and Iran in the Indian Ocean region.

Because the attack allegedly occurred outside the territorial waters of any country, it falls within the rules of naval warfare on the high seas and not as a violation of national sovereignty.

However, these incidents can still have serious geopolitical consequences, especially when they occur along major global shipping routes used for energy and trade.

(With contributions from agencies)