-3,646 m; ocean zones: Composed of water and in a fluid state, the ocean is delimited differently than the solid continents. It is divided into three zones based on depth and light level. Sunlight entering the water may travel about 1,000 m into the ocean under the right conditions, but there is rarely any significant light beyond 200 m.
The upper 200 m (656 ft) 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. Only a small amount of light penetrates beyond this depth.
The zone between 200 m (656 ft) and 1,000 m (3,280 ft) is usually referred to as the 'twilight' zone, but is officially the dysphotic zone. In this zone, the intensity of light rapidly dissipates as depth increases. Such a minuscule amount of light penetrates beyond a depth of 200 m that photosynthesis is no longer possible.
The aphotic, or 'midnight,' zone exists in depths below 1,000 m (3,280 ft). Sunlight does not penetrate to these depths, and the zone is bathed in darkness.