When rain on the ground and seeps below it, it washes away substances from the soil and rocks. It carries these substances into the river and the sea. You can read the names of these substances on the label of a bottle of mineral water. River water contains only a little salt-about 1 g/I, whereas the salt content of the sea is much higher-about 35 g/1, on an average. The reason is that the salt remains in the sea. Although the rivers continue to deposit new salts, the seas do not become ‘over salty’ because animals and plants in the sea absorb the salts in their bodies. When they die, they sink to the seabed and decompose into sediments.