There is a strange science involved in the mixing of waters. The phenomenon is different when two seas meet and different when fresh and salty water meet, and Quran has explained it all in clear details. Amazingly, after about 1400 years, the modern science has come up with all theories which certify the correctness of Quranic verses.

Modern Science has discovered that in the places where two different seas meet, there is a barrier between them. This barrier divides the two seas so that each sea has its own temperature, salinity, and density. [Principles of Oceanography – Davis, pp. 92-93]

For example, Mediterranean Sea water is warm, saline and less dense, compared to Atlantic Ocean water. When Mediterranean Sea water enters the Atlantic over the Gibraltar sill, it moves several hundred kilometers into the Atlantic at a depth of about 1,000 meters with its own warm, saline and less dense characteristics. The Mediterranean water stabilizes at this depth. [Principles of Oceanography p. 93]

The Mediterranean Sea water as it enters the Atlantic over the Gibraltar sill with its own warm, saline and less dense characteristics, because of the barrier that distinguishes between them. Temperatures are in degrees Celsius (C). Even in depths (indicated here by darker colors) up to 1,400 meters and at distances ranging from a minus -100 to +2,500 meters, we find that both bodies of water maintain their individual temperatures and salinity. Although there are large waves, strong currents, and tides in these seas, they do not mix or transgress this barrier.

The Holy Quran mentioned that there is a barrier between two seas that meet and that they do not transgress. God said:

He has granted freedom to the two great seas to meet [Noble Quran 55:19]

Yet there is a barrier in between which they cannot delete [Noble Quran 55:20]

A picture from the Gulf of Alaska shows a strange natural phenomenon that occurs when heavy, sediment-laden water from glacial valleys and rivers pours into the open ocean


But when the Quran speaks about the divider between fresh and salt water, it mentions the existence of “a forbidding partition” with the barrier.
God said in the Quran:

And He it is who has given freedom of movement to both the two great bodies of the water
One sweet and thirst allaying and the other salty and bitter
And yet he has set a barrier between them
And a ban forbidden
[Noble Quran 25:53]

One may ask, why did the Quran mention the partition when speaking about the divider between fresh and salt water, but did not mention it when speaking about the divider between the two seas?

Modern Science has discovered that in estuaries, where fresh(sweet) and salt water meet, the situation is somewhat different from that 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 discontinuity separating the two layers.“ {Oceanography, Gross, p.242. Also see Oceanography, Gross, p. 244 and Introductory Oceanography, Thurman, pp.300-301}.

This partition (zone of separation) has a different salinity from the fresh water and from the salt water. This information has been discovered only recently using advanced equipment to measure temperature, salinity, density, oxygen dissolubility, etc. The human eye cannot see the difference between the two seas that meet, rather the two seas appear to us as one homogeneous sea. Likewise the human eye cannot see the division of water in estuaries into the three kinds: the fresh water, the salt water, the partition (zone of separation).

But the question: why did God said (the two seas) not (the river and the sea) as we said before?

When scientists studied the seas, they found that rivers is not the only source of fresh water and that there are huge reservoirs of fresh water in and under the bottom of the oceans which continuously flows from the oceans’ bottom. And the volume of these huge reservoirs is as many times as what rivers flow into seas. So, each spring at the bottom of the ocean pumps a huge amount of fresh water which is as many times of what is pumped by that river.

Here, we realize why God be he blessed and exalted said (And it is He Who has let free the two seas) because there is a fresh and hidden sea which we don’t see with our eyes but it exists. This fresh water which flows from the bottom of oceans sometimes reaches the surface of water, goes for thousands of meters till it reaches the surface of water.

How can we invite non believers by towards Islam? It will be by introducing the realities of Quran to them. Since we live in the age of science, scientific technologies and scientific findings so the best way to invite non Muslims to Islam is the language of scientific truths which is included in Quran because when God be He blessed and exalted told us about this fact, it was for one target which is to make this fact as a weapon in Muslims’ hands to invite non Muslims to the way of God be He blessed and exalted.