Answer:
The sunlight that falls on the ocean surface in an open ocean, can penetrate up to a depth of about 200 to 300 m below the sea level.
Depending upon the depth the sunlight can penetrate, the ocean body is divided into 3 parts. They are as follows-
(1) Euphotic zone- This zone is also known as the sunlight zone. It extends up to a depth of about 200 meter below the sea level. this layer is comprised of most of the commercial fisheries and many other marine animals exist such as the turtles.
(2) Twilight zone- This zone is below the euphotic zone. It cover a vertical depth from 200 to 1000 meters below the sea level. The amount of light significantly decreases here due to the greater depth. The process of photosynthesis does not take place here due to the due to the absence of sunlight.
(3) Midnight (Aphotic) zone- This zone is the deepest part of the ocean where there is no sunlight and its totally dark. At the depth below 1000 meters is this zone and here very complex type of organisms are able to survive that can exist under the extreme pressure condition.
Thus, the amount of light decreases with the increasing amount of depth in the ocean.