system
Given the following post, respond as if you're commenting on Reddit:
human
If there was a body of water that was as deep as the Marianas Trench but perfectly clear and straight down, would you be able to see all the way to the bottom?
gpt
Even pure water absorbs and scatters light so you could not see the bottom of the 
Marianas Trench (10,994 m depth). The amount of sunlight in the ocean decreases exponentially from the surface.  The *extinction coefficient* varies with colors (wavelength) with the blues penetrating the deepest to a few hundred meters.  So even if you had the brightest floodlights in the Marianas Trench and perfectly ~~clear~~ pure water (the open ocean is pretty close except for the salinity),  you can't see anything more than a few hundred meters away.