What is the explanation to the Ayah where Allah states when salt water and sweet water go through each other and do not mix.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

Perhaps the questioner intends the following verse (which means): {And it is He Who has let free the two seas (kinds of water): this is palatable and sweet, and that is salt and bitter; and He has set a barrier and a complete partition between them.} [Quran 25:53] The meaning of this verse is that Allaah The Almighty, with His Power and Strength has set the two seas close and adjacent to each other so that they collide with one another, yet they do not combine. The water of one is palatable, sweet and fresh and quenches thirst, while the other is salt and with a strong concentration of saltiness, making it almost bitter. Allaah The Almighty has set a barrier between them, with His might so that one body of water does not mix or overtake the other, enabling a complete partition and avoiding any blending between them.

Furthermore, there are many verses mentioned in the Quran that are relevant to this discussion, such as, when Allaah The Almighty Says (what means):

However, the reality is that these verses and others similar to them clearly show us the might, ability and power of Allaah The Almighty in this Universe, and are from the miracles of the Holy Quran, and are facts, which clarify the Prophethood of the trustworthy Prophet Muhammad .

There have been many investigations about this matter by Muslim scholars, including Shaykh Abdul Majeed az-Zindani and Dr. Tariq al-Suwaidaan. Dr.Tariq al-Suwaidaan mentions in a speech about the miracles of the Holy Quran that this matter was kept undisclosed (i.e. the barrier between the two seas), with people being unaware of the truth about its purpose, until the year 1873 C.E. Thereafter, an English expedition by the name 'Challenger', was able to investigate the structural molecules of the two types of water and found that there were lines separating the two seas that could not be recognized by the naked eye. They also discovered that if you took a sample from both types of water and analyzed it, you would find differences in the structures, salt concentration and density. Furthermore, they even found differences in the marine life of the two seas, without the presence of a visible barrier. Hence, it is not an imaginary partition or a fanciful myth as some say; it is a reality.

However, the question remains: How can the two seas not blend and combine with each other while they are constantly moving and colliding with one another and waves and tides are rising from either side? Surprisingly this invisible barrier extends from the top of the sea to the bottom, constantly moving alongside the waves and tides avoiding any mixture between them. In 1984, researchers led by Dr. Muhammad Ibrahim, from the University of Qatar, conducted experiments and came up with the conclusion that the barrier was even clearer in the region between the Arabian Gulf and the Gulf of Oman.

Who taught this to Prophet Muhammad a person who had never sailed across seas? Who spoke about this isthmus in the Holy Quran, and the barrier that cannot be seen by the naked eye? Indeed, it is Allaah, the One, Who Says (what means): {We will show them Our Signs in the universe, and in their own selves, until it becomes manifest to them that this (the Quran) is the truth. …} [Quran 41:53]

Allaah Knows best.