Here's a breakdown:

* Pelagic zone: This encompasses all the water column of the ocean, from the surface to the seafloor, excluding the coastal and bottom regions.

* Oceanic zone: This is a broader term that refers to the vast, deep-water regions of the ocean beyond the continental shelves.

While the oceanic zone is a subset of the pelagic zone, the term "pelagic" is more precise when referring to the open ocean at any depth.