This is a scale diagram of the layers of the pelagic zone

The pelagic zone is the open sea or ocean that is not near the coast. The name comes from the Greek πέλαγος (pélagos), which might be translated as "open sea".

To make this clear, seas around continents have continental crust beneath them. They are shallow. Seas away from continents can be very deep, and do not have continental shelves beneath them.