The phrase "Seven Seas" is a figure of speech that has been used to refer to different bodies of water at various times and places throughout history. The origins of the phrase can be traced back to ancient times when it was used to describe bodies of water along trade routes, regional bodies of water, or exotic and far-away bodies of water. Some ancient civilizations used the phrase to describe the bodies of water known at that time. The ancient Romans called the lagoons separated from the open sea near Venice the septem maria or seven seas.

There is no definitive answer to what the Seven Seas are, as different cultures and time periods have used the phrase to refer to different bodies of water. However, the term can now be taken to refer to these seven oceanic bodies of water:

• The Arctic Ocean
• The North Atlantic Ocean
• The South Atlantic Ocean
• The Indian Ocean
• The North Pacific Ocean
• The South Pacific Ocean
• The Southern (or Antarctic) Ocean

It is worth noting that not all geographers agree on this list of seven, and some believe that the seven seas reference will be different depending upon the part of the world and the time period in question. For example, in Medieval European literature, the phrase referred to the North Sea, Baltic, Atlantic, Mediterranean, Black, Red, and Arabian seas.

Today, we recognize more than 50 seas worldwide, and a sea is defined as a division of the ocean which is enclosed or partially enclosed by land. With that said, the Caspian Sea, Dead Sea, and Aral Sea are actually saltwater lakes because they lack an outlet to the ocean. Conversely, by this definition, the Gulf of Mexico and Hudson Bay are seas.