In waters below the aphotic zone, a section of the water column from roughly 200 meters to 1,000 meters below the surface, no plants consistently grow. There is not enough light for plants, even phytoplankton, to carry out photosynthesis. Life below 1,000 meters in the oceans is sustained by falling organic matter, predatory existences and vertical migrations towards the surface to feed. In the ocean above 1,000 meters, plants such as sea grass, seaweed, kelp, algae and plankton thrive.
From the surface of the oceans and seas down to around 1,000 meters, plant life is varied and abundant. Sea grass and kelp anchor to the ocean floor or rocks, growing upwards towards the light. These plants are marked by broad, green leaves that are typically thick and fibrous. Algae grows both on rocks and other plants and flows freely in the water column. Phytoplankton grows in the water column, typically smaller than is visible to the human eye, and provides nutrients to many other sea creatures.
Below 1,000 meters, no sunlight penetrates the water. Below 200 meters, the amount of light varies depending on the sea or ocean and the severity with which the ocean floor falls away. Many of the same plants can grow between 200 meters and 1,000 meters but the density is much lower.