two bodies of flowing water

salam alaik.

verse 19 from sura al rahman stated that

He has let free the two bodies of flowing water, meeting together:

so, at river mouth, we often have this kind of phenomena, where the salty water from the ocean does not mix with the fresh water that comes from the river...

even we as humans cannot do that. if we try mixing two incompatible liquid, it will turn up to be a suspension and not a solution. but still two types of liquid do mix.

here we are talking about letting two different liquids flow freely without disrupting the ecosystem.

fishes from the seaside will not dare to enter the river, so do the fishes or any aquatic life from the river. due to different water pressure, the two bodies of flowing water do not mix.

subhanaLLAH