A more thorough explanation:

Internal waters refer to any natural or man-made body of water that is located within the territorial boundaries of a country. This can include bays, gulfs, river mouths, creeks, harbors, ports, lakes, and canals. These waters are also known as inland waters.

For example, the Great Lakes in North America are considered internal waters of the United States and Canada. Similarly, the Panama Canal is an artificial waterway that runs through Panama and is considered internal waters of the country.

The definition of internal waters is important because it determines the jurisdiction and control a country has over these bodies of water. Countries have the right to regulate and enforce laws within their internal waters, including fishing, shipping, and environmental protection.