Light travels about 1,000 meters down in the ocean

A diver "stands" on a ceiling of ice with thousands of feet of ocean water below his head. Sunlight only penetrates about 1.000 meters into the water, but almost all light dissipates after the first 200 meters.

Sunlight entering the water can only travel about 1,000 meters ( 3,280 feet) into the ocean.

The ocean is divided into three zones based on depth and light level. The upper 200 meters (656 feet) of the ocean is called the euphotic, or "sunlight," zone. This zone is penetrated by sunlight and plants thrive.

The zone between 200 meters (656 feet) and 1,000 meters (3,280 feet) is usually referred to as the “twilight” zone, but is officially the dysphotic zone. In this zone, the intensity of light dissipates as depth increases. At the lower depths, light penetration is very small.

The aphotic, or “midnight,” zone exists in depths below 1,000 meters (3,280 feet). Sunlight does not penetrate to these depths and the zone is bathed in darkness.

‘Photic’ is a derivative of ‘photon,’ the word for a particle of light.

For more information:
Light Penetration in Water, NOAA's Ocean Explorer