Legal Definitions - navigable sea

The term navigable sea refers to the vast ocean waters of the world, which are categorized under international law into distinct zones based on the level of control nations can exercise over them. These zones define the rights and responsibilities of countries regarding activities such as shipping, resource exploration, and security.

Under international law, the navigable sea is generally divided into three primary zones:

• Inland Waters: These are waters located on the landward side of a nation's baseline (often the low-water line along the coast), such as bays, harbors, estuaries, and rivers that flow into the sea. A nation has complete sovereignty over its inland waters, meaning it has full control, just as it does over its land territory.
• Territorial Waters: Extending typically up to 12 nautical miles seaward from the baseline, these waters are subject to the sovereignty of the adjacent coastal state. However, this sovereignty is limited by the right of "innocent passage," which allows foreign vessels to travel through these waters peacefully, without posing a threat to the coastal state's security or violating its laws.
• High Seas: These are all parts of the sea that are not included in the inland waters or territorial waters of any state. The high seas are international waters, meaning no single nation has sovereignty over them. They are open to all states for activities like navigation, overflight, fishing, and scientific research, subject to international law.

Here are some examples illustrating the concept of navigable sea:

• Example 1: A Cruise Ship's Journey to Port

  Imagine a large cruise ship departing from one country and heading to a port in another. As it approaches its destination, the ship first enters the host nation's territorial waters. During this phase, the cruise ship has the right of innocent passage, meaning it can transit peacefully without stopping or engaging in activities unrelated to passage. However, it must comply with the coastal state's laws, such as those concerning pollution or navigation safety. Once the ship enters the specific bay or harbor where it will dock, it has moved into the nation's inland waters. At this point, the coastal nation exercises complete sovereignty, requiring the ship to undergo customs inspections, adhere to port authority regulations, and potentially take on a local pilot to navigate the harbor safely.

• Example 2: Marine Scientific Research

  Consider a marine biology research vessel from Country A that wants to study deep-sea ecosystems. If the vessel conducts its research far from any coastline, in the vast expanse of the ocean, it is operating on the high seas. Here, it generally has the freedom to conduct scientific research without needing permission from any specific nation, provided it complies with international regulations. However, if the research team wishes to collect samples or deploy equipment within 10 nautical miles of Country B's coast, they would be entering Country B's territorial waters. In this scenario, the research vessel would need to obtain explicit permission from Country B, as Country B has sovereign rights over those waters and can regulate scientific activities within them, even if innocent passage is generally allowed for transit.

• Example 3: Naval Patrol and Enforcement

  A navy patrol boat from Country C spots a suspicious vessel that appears to be engaged in illegal fishing. If the patrol boat encounters the vessel 200 nautical miles offshore, both are on the high seas. In this situation, the patrol boat can only board and inspect the suspicious vessel if it is registered to Country C (its flag state) or if there's a specific international agreement allowing such action (e.g., anti-piracy operations). However, if the same suspicious vessel is observed fishing illegally just 5 nautical miles from Country C's coast, it is clearly within Country C's territorial waters. Here, Country C's navy has full authority to intercept, board, and arrest the crew, as Country C exercises complete sovereignty over its territorial waters and can enforce its national laws, including those against illegal fishing.