What Makes a Sea a Sea?

While the definition of a sea is not completely set in stone, a sea is generally defined as a portion of the ocean that is partly surrounded by land. In some cases, a sea is completely landlocked, such as the Caspian Sea, which lies between Russia and Iran, and which is also referred to as the world’s largest lake. The Aral Sea and the Dead Sea are also surrounded by land and contain salt water, but many oceanographers consider them lakes. This leaves dozens of water bodies that fit the traditional definition of a sea despite being quite different from one another. A sea can be more than 2.6 million square kilometres in area, such as the Caribbean Sea. Or, it can be as tiny as the Sea of Marmara, a Turkish body of water of less than 12,950 square kilometres that connects the Aegean Sea and the Black Sea.