“And it is He Who has let free the two seas (kinds of water), one palatable and sweet, and the other salty and bitter, and He has set a barrier and a complete partition between them.” Allah, the Almighty, says: “And it is He Who has let free the two seas (kinds of water), one palatable and sweet, and the other salty and bitter, and He has set a barrier and a complete partition between them.” (Al-Furqan: 53)
The Scientific Fact:
The first book on oceanography during the 18th century contained very simple information. When the British ship Challenger took its voyage all over the world between 1872 and 1876, oceanography started to take its position amongst other modern sciences. This was followed by many scientific voyages that were launched to explore oceans and seas. At the end of the 20th century, man sought more understanding of oceanography through the use of satellites and aerial photography. After closely surveying many points where rivers join seas, researchers discovered that the river mouth is always a very distinguished area having its own characteristics that are different from those of the sea and those of the river itself. This fact highlights the point that the sweet water of the river does not mix with the salty water of the sea. There appears to be some kind of barrier that separates both waters and enables each to maintain its own qualities. Categorizing the three areas (i.e. river, sea, and river mouth) based on the living organisms in each, researchers discovered that certain creatures only live in the river mouth and cannot live outside it. By the same token, creatures of other areas cannot live in this area of the river mouth due to its own special characteristics.
Facets of Scientific Inimitability:
Any gathering of water can be called a ‘sea’ and if the water is sweet, it is given the name ‘river’; and if salty, it is ‘sea’ or ‘ocean’. The water found in the river mouth areas is not included here since it is a mixture of sweet and salty water. Therefore, we can distinguish three kinds of waters; sweet water in rivers, salty water in seas, and a mixture in river mouth areas. Such areas are described as having barriers and complete partitions that halt any flow of water between the water of the river and that of the sea. It is also known as being the culture of certain marine creatures that cannot live outside such areas.
The history of oceanography testifies to the fact that no accurate information about oceans and seas existed fourteen centuries ago. Yet, the Ever-Glorious Qur’an gave a full accurate account of the river mouth areas and showed the characteristics of these distinguished areas. The Ever-Glorious Qur’an explained that, with the non-stop movement of the water in such areas, they formulate a barrier between the sweet water of the river and the salty water of the sea. This Qur’anic description was given a long time ago before the invention of the modern technology.
Source: https://www.islamland.com/eng/articles/river-mouths