“Or (the unbelievers’ state) is like the darkness of a fathomless sea which is covered by waves above which are waves above which are clouds, layers of darkness, one upon the other. If he puts out his hand, he can scarcely see it. Those God gives no light to, they have no light.” Allah, the Almighty, said: [Or (the unbelievers’ state) is like the darkness of a fathomless sea which is covered by waves above which are waves above which are clouds, layers of darkness, one upon the other. If he puts out his hand, he can scarcely see it. Those God gives no light to, they have no light.] (An-Nur:40)
The Scientific Fact:
The Encyclopedia Britannica states that oceans and deep seas are mostly covered by thick cumulus clouds, which hinder a large amount of sun light, as shown in satellite pictures. These clouds reflect most sunrays and prevent some of its light; water reflects some of the light that comes to earth and absorbs the rest that gradually decreases with depth. Thus, levels of darkness in the water in a depth of 200 meters are created and darkness reaches its peak below a depth of 1000 meters; no light can be seen at all. The Secchi disk was the first piece of equipment for measuring light in deep oceans.
Scientists discovered kinds of fish in (600-2700 meters) deep water that use luminous organs to enable them to see in the dark so as to catch their prey.
Modern marine sciences, at the end of the 19th century, discovered, after using developed pictorial equipment, internal rough waves in deep seas. These waves are located in the surface separating every two layers of water and are different in density, pressure, heat, and ebb and flow.
Scientists have recently discovered that there are internal waves that occur on density interfaces between layers of different densities. These internal waves cover the deep waters of seas and oceans because deep water has a higher density than the water above it. Internal waves act like surface waves. They can break, just like surface waves. Internal waves cannot be seen with the naked eye.
The exhausted energy used in the process of generating these waves equals the energy of sailing a ship; therefore, many ships in this area suddenly lose control because of stagnant water that was first discovered by the Swedish professor V. W. Ekman in the beginning of the 20th century.
Facets of Scientific Inimitability:
Previously, mankind believed in superstition concerning deep seas and oceans and there was not enough scientific information about the reality of the depth of water and water currents. Although they knew that wind currents affect surface waves, they had no knowledge about internal waves.
This honorable verse referred to the darkness inside deep seas by using the expression (fathomless sea) and mentioned that the darkness in these seas consists of layers. The interpreter of the Ever-Glorious Qur’an stated that the layers of darkness mentioned in this verse are the darkness of clouds, the waves, and the sea; one can see nothing in these layers.
Dense clouds that cover the seas reflect some of the sun’s light and the surface of the sea reflects some others and then the water absorbs almost all the seven colors of the light spectrum, one after another. Afterwards, internal waves turn the bottom into complete darkness, where there is no light at all; to the extent that one cannot see one’s own hand.
In addition, the statement in the verse “…like the darkness of a fathomless sea which is covered by waves above which are waves above which are clouds…” draws our attention to another miracle of how the Ever-Glorious Qur’an accurately describes the sea.
Fish in these depths have no eyes; they have luminous organs in their bodies to enable them to see in the darkness, as He (Exalted and Glorified be He) says, “Those God gives no light to, they have no light.”
The honorable verse also indicates the internal waves in the area between two layers of water of different density. This scientific fact that was declared in the verse fourteen centuries ago has recently been discovered by scientists.
Then who told Prophet Muhammad (peace be upon him) this but the All-Aware, the Most High?
Source: https://www.islamland.com/eng/articles/properties-of-deep-seas