Al Furqan Ayah 53

۞ وَهُوَ ٱلَّذِى مَرَجَ ٱلْبَحْرَيْنِ هَـٰذَا عَذْبٌ فُرَاتٌ وَهَـٰذَا مِلْحٌ أُجَاجٌ وَجَعَلَ بَيْنَهُمَا بَرْزَخًا وَحِجْرًا مَّحْجُورًا ٥٣ And He is the One Who merges the two bodies of water: one fresh and palatable and the other salty and bitter, placing between them a barrier they cannot cross.