Which seas are the smallest?

It depends on when you ask this question. At various times and to various cultures the "Seven Seas" have been different:

• In Greek literature the Seven Seas were the Aegean, Adriatic, Mediterranean, Black, Red, and Caspian seas, with the Persian Gulf thrown in as a "sea."
  
• In Medieval European literature they were the North Sea, Baltic, Atlantic, Mediterranean, Black, Red, and Arabian seas.
  
• After the 'discovered' North America the Seven Seas were the Arctic, the Atlantic, the Indian, the Pacific, the Mediterranean, the Caribbean, and the Gulf of Mexico.