Where does the salt in seawater come from Salt like sand comes from the breakdown of rocks. Some types of rocks and minerals are made of salt and when they are eroded or broken down the particles of salt dissolve in water. When water evaporates out of the oceans the salt is left behind to keep the ocean water salty.
Little freshwater is added to the volume of the oceans so the seawater maintains it's salinity.
Salinity tells us how much salt is in water. The higher the salinity value the more salt is in the water. Average seawater is 35 parts per thousand.