Deep Waters

Scientifically, it is well-known that visible light cannot penetrate deep into the ocean. As one descends into the ocean's depths, the amount of light decreases progressively until it becomes completely dark. 

In the Quran, specifically in Chapter An-Nur (Chapter 24, Verse 40), there is a description of a similar phenomenon:

"Or like the depths of darkness in a vast deep ocean, overwhelmed with waves topped by waves, topped by clouds: depths of darkness, one above another: if a man stretches out his hand, he will not see it!"

This Quranic verse vividly describes an environment of profound darkness in the deep sea, where even if a person were to stretch out their hand, they would not be able to see it due to the absence of light.