Muslims present the following Verse from Quran as a miracle:
Allah says,

“God is the one who caused two bodies of water to flow, one palpable and sweet, the other salty and bitter.
He placed a barrier between them, a partition that they are forbidden to surmount”. ( Quran 25:53)

Did you know that Science only became aware of this phenomenon in 1965, after the satellite Gemini 4 photographed the Nile Delta.

 

This verse is not a Quranic miracle, but one of the biggest proof that author of Quran was so much ignorant of the science. 

First: Wrong Translation:

The author of Quran used the word "Two Bahrain بحرین", which means "Two Oceans". But since Oceans always have salty water, therefore Muslims got no answer to it where does this ocean of sweet water exist. Therefore, they cunningly changed the translation from "Two Bahrain" from two oceans to "two bodies of water", and then called the sweat Nile delta as one of them.

Till this century, none of the Muslim Mufassir of Quran ever come to conclusion that God is talking about Nile Delta, but for the last 14 centuries, these Muslim Mufassirin (commentators) had other theories about these two oceans.

 

Ignorance of author of Quran from where does the rain water comes

People of earlier centuries didn't know how water evaporates and how clouds are formed from which rain water comes. Therefore, they made a false assumption that there is an Ocean of Sweet Water on the heaven, and sweet rain water comes from that ocean on the heaven.

Same assumption was also made by the author of Quran. And from here came the Islamic claim that "Throne of Allah" is also established upon the water (i.e. water above the 7 heavens, and above the water there is throne of Allah).

Therefore, the author of Quran is repeating this fantasy story in this Quranic Verse of two Oceans, one salty and one sweet.

The Sahaba (companions) mentioned the same 2 oceans (one in heaven and one on earth) in commentary of this verse.

Tafsir al-Qurtabi (Commentary of Verse 25:53):
وقال ابن عباس وابن جبير: يعني بحر السماء وبحر الأرض.
قال ابن عباس: يلتقيان في كل عام وبينهما برزخ قضاء من قضائه. { وَحِجْراً مَّحْجُوراً } حراماً محرّماً أن يعذب هذا الملح بالعذب، أو يملح هذا العذب بالملح.
Translation:
Companion Ibn Abbas and Ibn Jubair said: "In these verses 2 Oceans mean one from the heavens and one from the earth"
Companion Ibn Abbas said: (Yultaqyaan) means they meat with each other every year, but still there always exists a barrier between them, and thus salty water didn't become sweet and vice versa.

And also:

Tafsir Dur-e-Manthus (Commentary of 25:53):
وأخرج ابن أبي حاتم عن الحسن في قوله { مرج البحرين } قال: بحر في السماء وبحر في الأرض
Translation:
Ibn Abi Hatim and Hassan Basri said: In this verse it is meant one Ocean on the heavens and one on the earth.

This is the Commentary which was given by Sahaba and Tabaeen.

Therefore, it becomes clear which fantasy story was going in the mind of the author of Quran, as he was telling this verse.

This same Quranic Model has been earlier told by Bible too, where again the sweet water ocean is on the heavens and from there comes the sweet water of rain.

Sweet Water Ocean in Bible

And this is Sumerian Cosmology, and again we find the same thing here where sweet water Ocean is on the heaven and from there comes the sweet water of rain when the gates of heavens are opened.

Sweet Water Ocean in Sumerian Cosmology

And the author of Quran again told the same fantacy story in Quran at another place:

(Quran 23:18) وَأَنزَلْنَا مِنَ السَّمَاءِ مَاءً بِقَدَرٍ فَأَسْكَنَّاهُ فِي الْأَرْضِ ۖ وَإِنَّا عَلَىٰ ذَهَابٍ بِهِ لَقَادِرُونَ
Translation:
And we send down from the sky (sweet) water in "measure", and We give it lodging in the earth, and lo! We are Able to withdraw it too (so that constant amount of sweet water stays on earth and it does not cause floods on the earth due to this excessive sweet water from the Ocean on the heaven).

This translation is by Pickthal, with parenthesis from our side to make things clear.

So, you could see that author of Quran didn't know about that rain water comes from evaporation from the water which is already present on the earth.

But the author of Quran thought that rain water comes from the sky (from the ocean of sweet water on the heavens). And then God had to sent this water only in a "measured quantity" to stay on the earth. And since sweet water has been coming constantly from the sky for thousands of years, thus whole world should have already been flooded with the water, therefore, God then had to take away/withdraw this extra water on the earth too.

Are you able to see the pseudo-science in Quran now?

We again find that Ahadith are also mentioning this sweet water on the heavens:

Sahih Bukahri, Book of Merits of Ansar (link: https://sunnah.com/bukhari/63/113):
... then Holy Prophet said: ' Then I was made to ascend to Sidrat-ul-Muntaha (i.e. the Lote Tree of the utmost boundary) Behold! Its fruits were like the jars of Hajr (i.e. a place near Medina) and its leaves were as big as the ears of elephants. Gabriel said, 'This is the Lote Tree of the utmost boundary) . Behold ! There ran four rivers, two were hidden and two were visible, I asked, 'What are these two kinds of rivers, O Gabriel?' He replied,' As for the hidden rivers, they are two rivers in Paradise and the visible rivers are the Nile and the Euphrates.'

Today, we have been asking the Muslims how come the water of Neil and Euphrates comes from Sidrat-ul-Muntaha (which is above the 7 heavens). But Muslims don't reply.
Why?
Because Muslims are unable to tell the fanstacy story today that God makes the sweet water at Sidratul-Muntaha to rain down from heavens to Neil and Euphrates.

Here is another hadith about it: 

Sahih Muslim, Book of The Book of Paradise, its Description, its Bounties and its Inhabitants (Link: https://sunnah.com/muslim/53/30):

Abu Huraira reported Allah's Messenger (may peace be upon him) as saying: Saihan, Jaihan, Euphrates and Nile are all among the rivers of Paradise.