NABA wrote: the best example of this verse can b seen when Mediterranean sea meets with Atlantic ocean,the water of Mediterranean sea is more warm less dense as compared to Atlantic when water of Mediterranean enters Atlantic even at the depth it maintains its original characteristic,explained in principles of oceanography p 93.Allah U Akbar!!!!

Ocean Mixing

Mixing in the ocean occurs on several scales, the smallest scale being molecular. If a layer of warm, salty water lies above a layer of colder, fresher water, the heat and salt will tend to diffuse (spread out) downwards to make a single layer with intermediate temperature and salinity values. However, because heat diffuses faster than salt, the process can lead to local instabilities in the density structure which cause mixing within a layer many meters thick. The best-known example of this process, known as salt fingering, occurs where very salty water from the Mediterranean outflow mixes into the North Atlantic.

http://www.encyclopedia.com/doc/1G2-3409400232.html

55:19,20 and 25:53 reflect a misunderstanding of nature. There is no complete partition or barrier between the seas, that neither of them dare to transgress. They meet each other, and within a certain layer that is then formed, they mix. This layer is many meters thick. They very much indeed 'transgress'.

Also, neither the Mediterranean Sea or Atlantic Ocean are sweet or palatable, to the best of my knowledge. One is less salty than the other, but both are salty.

Allahu Akhbar! All praise be to Allah- the Father, Son and Holy Spirit!