Sodium chloride washes into the oceans around the globe from rivers and streams. Over time the abundant salt(notice I said abundant) has been deposited into the world's oceans and remained there . Even fresh water has some salt in it, but not near as much as ocean water. Water is replenished by evaporation over the oceans and the heavy salt remains behind and mixes with the fresh new water from the cyclical rainfall.The ocean's creatures need the salt water as their environment and cannot live, without it, with the exception of a few fish that migrate in fresh water streams to lay eggs, and some sharks, such as the Bull Shark. The salt or sodium chloride was washed from deposits in the earth, just as other chemicals and elements have been over millions of years. The salt evidently is one of the hardiest, and remains a part of the ever-evolving cycle of life on the planet.