Why Is The Water In The Sea Salty?

Seawater, on average, has a salinity of ~3.5%. This means that for every 1 litre of seawater there are 35 grams of salts dissolved into it (this is mostly, but not entirely, sodium chloride).

The freshest seawater (least saline) on the planet can be found in the eastern parts of Gul of Finland and in the northern end of Gulf of Bothnia, both part of the Baltic Sea.The Red Sea is the most saline open sea, where high temperatures along with confined circulation result in high rates of surface evaporation and there is little fresh inflow from rivers. In the Dead Sea, and other isolated or salt-water lakes, the salinity can be considerably greater.

Sir Edmund Halley started the scientific theories behind the origins of sea salt in 1715, proposing that salt and other minerals were carried into the sea by rivers, having been leached out of the ground by rainfall runoff.

Water is saline everywhere even in lakes and rivers. It's just that the level of salinity in rivers is so low it is hardly recognized by human tongue.

Over millions of years the rainwater pouring on rocks have taken the rock salts along with them to the rivers and from their on to Oceans. From Oceans the water evaporates leaving the salts behind, gradually increasing the level of salinity to 4-6%.

But on the other hand, the ongoing rock formation under the seas have kept this level almost stagnant over the years.

You will be fascinated to know that there are seas in the world where salt levels are as high as 49% which is 10 times the average salinity of sea water

It was because the fishes need oxygen