Here we see the divider between theMediterranean and the Atlantic ocean.  In the middle of this photo we see a colored triangle, this is the base of the rock of Gibraltar. We can observe a colored partition between the two bodies of water, although the naked human eye cannot perceive it in nature.

Traditionally, there have been two major interpretations of this verse. The Qur’aan goes on to state that there is barrier between them, means that this  barrier will simply prevent the seas from encroaching upon each other or flooding over each other.

Proponents of the second opinion ask how can there be a barrier between the seas so that they do not encroach upon each other, while the verse indicates that the seas meet together? They concluded that the seas do not meet and sought another meaning for the term "maraja". But now modern science provides us with enough information to settle this issue. The seas do meet together, as we have seen, for example, in the picture of the Mediterranean and Atlantic Ocean. Even though there is a slanted water barrier between them, we now know that through this barrier the water from each sea passes to the other.

 But when we the water from one sea enters the other sea, it looses its distinctive characteristics and becomes homogenized with the other water. In a way, this barrier serves as a transitional  homogenizing area for the two waters. This is an excellent example of Islamic modern scientific research. Modern techniques can thus be used to prove the inimitability of the  Qur’aan. 
 

Modern Science has discovered that in estuaries, where fresh (sweet)  and salt water meet, the situation is somewhat different from what is found in places where two seas meet.

It has been discovered that what distinguishes fresh water from salt water in  estuaries is a ”pycnocline zone with a marked density. 
(2) discontinuity seperating the two layers.” This partition (zone of seperation)  has a different salinity from the  fresh water and from the salt water (3)
“He is the one who has let free the two bodies of flowing water, one  palatable and sweet, and the other salty and bitter. And He has made  between them a barrier and a FORBIDDING PARTITION.” QURAN (25:53)

DARKNESS IN A DEEP SEA
 

“ Or is like the darkness in a deep sea. It is covered by waves, above which are waves, above which are clouds. Darkness, one above another. If a man  stretches out his hand, he cannot  see  it...” QURAN (24:40)

 The darkness in deep seas and oceans is found around a depth of 200 metres and below. At this depth, there is almost no light.  Below  a dept of 1000 metres there is no light at all. (4) 

WAVES ABOVE WAVES 

“ Or is like the darkness in a deep sea. It is covered by waves, above which are waves, above which are clouds. Darkness, one above another. If a man  stretches out his hand, he cannot  see  it...” QURAN (24:40) 

 Scientists have only recently discovered that there are internal waves  which “occur on density  interfaces between layers of different densities. (5) 

The internal waves cover the deep waters of  seas and oceans because the deep waters have a higher density than the waters above them.  Internal waves act like surface waves. They can also break just like surface waves.  Internal waves cannot be seen by the human eye,  but they can be detected by studying  temperature or salinity changes at a given location. (6)

(1) Principles of Oceanography, Davis, Page:92-93 
(2) Oceanography, Gross, Page:242 
(3) Oceanography, Gross, Page:244 
(4) Oceans, Elder and Pernetta, Page:92-93 
(5) Oceanography, Gross, Page:205 
(6) Oceanography, Gross, Page:205