Euphotic

The ocean is divided into three zones based on depth and light level. The upper 200 meters of the ocean is called the euphotic, or "sunlight," zone. This zone contains the vast majority of commercial fisheries and is home to many protected marine mammals and sea turtles.

The corals’ requirement for high light also explains why most reef-building species are restricted to the euphotic zone, the region in the ocean where light penetrates to a depth of approximately 70 meters.