Not to worry, landlubbers, you can still be a salty dog on either, but here is the difference; if you are on a sea, you are partially enclosed by land on some part of your border, while if you are on an ocean, you could be a speck with 1000’s of kilometres separating you from sweet solid ground. Seas are smaller, shallower bodies of water, partially surrounded by a chunk of land; the Bering Sea is bordered by Russia and the United States. The Mediterranean Sea is bordered by Southern Europe, Asia, and Africa and considered to be the largest sea in the world. Seas can also be completely enclosed by land as is the case with the Black Sea and the Dead Sea.
What about gulfs; like the Gulf of Mexico and the Persian Gulf. What is the difference between seas, oceans and gulfs? The Newberry Library definition provides the most clarity to this question: “a body of water existing within a large embayment of a continental coastline.” A bay, therefore is like a gulf but smaller scale.