Ocean vs. Sea: What’s the Difference?

The primary difference between an ocean and a sea lies in their size and depth, with oceans being larger and deeper than seas. Oceans are vast bodies of saltwater that cover nearly 71% of Earth’s surface, with an average depth of about 3,688 meters (12,100 feet). In contrast, seas are smaller and shallower, often partially enclosed by land. For instance, the Atlantic Ocean covers approximately one-fifth of Earth’s surface, while the Mediterranean Sea, a well-known sea, is significantly smaller.

Oceans are not confined by land and are continuous expanses of water. Seas are often located on the margins of oceans and are partially enclosed by land, such as the Mediterranean Sea, which is bordered by Europe, Asia, and Africa. This geographical distinction makes seas more accessible and often more influenced by human activities; seas also tend to have historical, political, and sometimes ecological significance.