“It is We Who have sent down the Dhikr (The Quran) and surely, We will guard it (from corruption).” (15:9)
Collection: Deep Waters
Recent studies have demonstrated that Visible light cannot penetrate deep waters. In deep waters, it is very dark as little to no sunlight penetrates the water, and the deeper you go, the darker it gets.
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! If Allah does not give light to a person he will not have light!
The Quran says that it is so dark down there you cannot see your own hand.
Bear in mind, a person could not have entered deep oceans around the time the Quran was revealed (1400 years ago)