Is there a place in the world (in some sea or ocean) where saltwater and freshwater meet but don't mix?

Question

I was told that this phenomenon is mentioned in the Qu'ran, and that it has been confirmed in modern science that there is a place in the sea where this happens. Any idea where?

Answer 1

Yes.
Although this is a trick.
In some places you have ice (which is solid fresh water) floating in the sea.
In the case of liquid water you have many rivers that run into the sea. There is a gradient of salt from the sea back into the river, but since their is a current the salt only goes back into the river so far. In this case the transition from salt water to fresh water is smooth (the salinity decreases slowly as you move up-river).

Answer 2

There is one class of places where salt water and fresh water meet, but dont mix: In underground aquifers.

For example, Where there are sand dunes next to the sea, and the climate is not arid; rainwater landing on the sand surface percolates down till it meets the underlying saltwater aquifer. Because fresh water is lighter that salt water, the fresh water lies on top, without mixing. The low permeability of the sand helps keep the two apart, because the movement of the water through the sand is quite slow. What will eventuall happen is that the fresh water will flow sideways across the top of the saltwater, until it reaches the edge of the dunes, and they eventually mix. But the salt water / fresh water interface is quite stable.

The fresh water can even be drawn off through a bore, providing the bore does not strike the salt water. It is one of the tasks of a geohydrologist to make sure that any such bores are managed properly, so that the interface is not disturbed.

Edit: Centretek666 is quite right; that is another example, where an underground saltwater/freshwater interface is quite stable. There are similar caves and limestone beds in Western Australia, and I would imagine elsewhere.

Answer 3

Places where major rivers enter the sea. Fresh water being less dense than salt water means that the fresh water tends to move across the surface of the salt, apparently without mixing.

The mention in the Holy Qu'ran probably refers to the mouth of the Tigris-Euphrates river system, at the Shatt-el-Arab, at the head of the Persian Gulf, or to the mouth of the Nile at the Eastern end of the Mediterranean Sea.

Answer 4

There are limestone caves at Narracorte in South Australia where the bottoms of the caves are open to the sea, because there is no wave action inside the caves the fresh water from rain, sits on top of the saltwater( salt water is heavier than fresh).