One of the most well-known qualities of the ocean is that it is salty. The two most common elements in seawater, after oxygen and hydrogen, are sodium and chloride. Sodium and chloride combine to form what we know as table salt. Of the five ocean basins, the Atlantic Ocean is the saltiest. On average, there is a distinct decrease in salinity near the equator and at both poles, although for different reasons.

Source: NOAA