What Is the Difference Between an Ocean and a Sea?

Depth, area, and marine life differentiate oceans from seas.

An ocean is a vast and a continuous frame of salty water that shelters almost 70 percent of the total earth's surface while a sea is a large body of saline water that occupies a greater part of the world's surface but is smaller than an ocean. The difference between the two water bodies is summarized in in terms of depth, area, and marine life.


As stated earlier, oceans are large water bodies that exist on the earth's surface. There are five different oceans, the Pacific Ocean being the largest with a depth of around 10,924 meters, and the Arctic Ocean is the smallest with a depth of 5,625 meters. The five oceans join together to form one large body of saline water commonly known as the world ocean, which has an average depth of 3,688 meters. On the other hand, there are different types of seas with most common ones being the Mediterranean Sea, Baltic Sea, North Sea, Bering Sea and the Red and Yellow Seas. The major seas are the Caribbean Sea, the South China Sea, and the Mediterranean Sea. The Caribbean Sea is the deepest sea with an approximate depth of 6,946 meters.The comparison by depth shows that oceans are much deeper as compared to seas because land usually encloses the seawaters.


Oceans are the most prominent water bodies on planet earth with an average total area of 361,900,000 square kilometers. The largest ocean is the Pacific Ocean which covers an area of 60,060,700 square miles, while the smallest ocean (Arctic Ocean) is estimated to cover an area of 5,427,000 square miles. On the other hand, the largest sea, which is the Mediterranean Sea has an area of 1,144,800 square miles, a smaller area than that of the smallest ocean. Thus, this variation in the area indicates that seas are smaller than oceans.

Marine Life

The plants and animals that exist in salty waters (oceans and seas) are the ones that make up marine life. The distance from the shore of the ocean or sea and their depths intensely impact the quantity and biodiversity of aquatic plants and sea creatures that exist here. Since seas are permanently around the land, aquatic existence is abundant, but this is not the case with oceans. Oceans are deeper than seas and farther away from land thus reducing aquatic life in them. The basic life forms that exist on oceans include microscopic planktons, bacteria, and shrimp. Seas support a large portion of marine life since sunlight penetrates deep down allowing photosynthesis to take place. Oceans rarely support marine life since they are deeper than seas and thus sunlight does not penetrate deep enough to the surface to let photosynthesis to take place.

Essential Difference

In conclusion, the essential difference between oceans and seas is that oceans are massive saline water bodies that exist on the Earth's surface while seas are vast saline waters that are either connected or not connected to the ocean. The terms oceans and seas are often used interchangeably since they almost mean the same thing. It is, therefore, necessary to note these differences while talking about seas and oceans.

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