Do the oceans have real boundaries?
While there’s only one world ocean, maps recognize five different oceans and several more seas worldwide. How can we distinguish them? Are there “real” borders or boundaries between them? Do the waters of different oceans really get mixed?
Imagine for a moment that you spend your holidays in the sunny coast of Croatia. You are swimming in the crystal waters of the Adriatic sea when you start thinking about if you are having a bath also in the waters of the Mediterranean sea.
Are they the same? If so, why do they have different names? And, if they are not the same, why? Is there any physical border or boundary between two distinguishable bodies of water?
Let’s start from the scratch. The same way all continents of the Earth were once a single huge continent named Pangaea, all the oceans belong to a single world ocean (Panthalassa), as the waters of all of them —and the rest of the smaller seas— are connected through straits or just open currents all over the globe. There is only one case where the continental drifting left one sea enclosed and so its waters disconnected to the world ocean, that is the Caspian sea.
