Difference between Sea and Ocean

January 14, 2017 by Editorial Team

Where do you see yourself when you imagine spending a vacation? Lounging in a hammock on the beach? Gazing at the waves of a sea or of an ocean? While it may not matter for your fantasy, seas and oceans differ and you should not use them interchangeably. You do not need to be a geographer to know the difference between a sea and an ocean; a 3rd grader knows. Do you?


Map comprising six of the Balkan region seas

A sea is a large body of salt water surrounded by land or connected to another sea or an ocean. In some cases, a sea can have land on all sides, like the Caspian Sea or the Dead Sea, which are practically saline lakes with no communication with other bodies of water. Or a sea can be part of an ocean, like the Sargasso Sea in the North Atlantic Ocean.

There are close to 100 seas on Earth. The largest one is the Philippines Sea with an area of 2,000,000 square miles, an average depth of 5,419 feet and a maximum depth of 34,578 feet. The smallest sea is the Gulf of California, also known as the Sea of Cortez, with a surface area of 62,000 square miles.

Map of the Atlantic Ocean

An ocean is an immense body of saline water. Oceans cover around 70% of the Earth’s surface. We can name 5 different oceans: Arctic, Atlantic, Pacific, Indian and Antarctic – 7 if you count the North-South portions of the Atlantic and of the Pacific as separate areas. These are all part of what we call the World Ocean as these bodies of water communicate with each other.

The largest ocean is the Pacific, covering an area of more than 60,000,000 square miles. Its average depth is 13,215 feet. The Mariana Trench is the Pacific Ocean’s deepest point at 36,198 feet below sea level. The smallest ocean is the Arctic Ocean, with a surface area of 5,100,000 square miles, an average depth of 3,953 feet and a maximum depth of 18,456 feet in the Eurasia Basin.


While they are both roughly the same thing, it is size that makes all the difference between them. Seas are great bodies of salt water whereas oceans are even bigger bodies of salt water that sometimes include the seas. A sea can be bound by land on some or all parts, and it can communicate with other seas or directly with an ocean. On the other hand, all oceans communicate and make up the World Ocean.

Given their sizes, there are 5 big oceans and up to 100 seas. Also, the presence of marine life in oceans and seas strongly depends on the depth of the water and the distance from the shores. This makes seas more prolific when it comes to providing an environment that supports life.

Comparison Chart

A large body of saline waterAn immense body of saline water
Can be bound by land on all sides or on some sides; can communicate with another sea or with an oceanCan contain seas; communicates with other oceans
The biggest sea has an area of 2,000,000 square milesThe biggest ocean has an area of 60,000,000 square miles
The smallest sea has an area of 62,000 square milesThe smallest ocean has an area of 5,100,000 square miles
There are more than 100 seasThere are 5 oceans
Better suited for marine lifeLess fit to sustain life forms