Is sea water referred to as hard water?

Sea water is not considered hard water. Hardness of water is determined by the concentration of dissolved minerals, primarily calcium and magnesium ions. Seawater contains these ions, but their concentration is not as high as in hard water. Additionally, the presence of other dissolved salts and minerals in sea water, such as sodium and chloride, tends to counter the effects of calcium and magnesium ions, resulting in a lower overall hardness.