oceanic zone definition
Understanding Ocean Zones: The Sunlight Zone. This ocean zone is from the surface of the sea down to a depth of about 200 meters. As you begin your descent you see that the ocean is absolutely teeming with life forms of every sort. From the microscopic plankton and diatoms that give the ocean its murky color and limits visibility, to bony fishes of every shape and size, to starfishes, and warm-blooded, oxygen-breathing mammals.