Sea water is salty because the amount of salt present in it very high compared to any other liquid which gives it a salty taste....To test the present of salt in sea water take some in a plate and dry it and you will find the solid particles left behind is grains of salt....
because sea water contains high amount of salt and other minerals in it.these minerals and salt is useful for those beings which live in sea. Also the salt which we use at home is prepared from the sea water evaporation.
Most of the salt in the oceans came from land. Over millions of years, rain, rivers, and streams have washed over rocks containing the compound sodium chloride (NaCl), and carried it into the sea. You may know sodium chloride by its common name: table salt! Some of the salt in the oceans comes from undersea volcanoes and hydrothermal vents. When water evaporates from the surface of the ocean, the salt is left behind. After millions of years, the oceans have developed a noticeably salty taste.