Why Is The Ocean Water Salty?

The rain that falls on the land contains some dissolved carbon dioxide from the surrounding air. This causes the rainwater to be slightly acidic due to carbonic acid (which forms from carbon dioxide and water). The rain erodes the rock and the acid breaks down the rocks and carries it along in a dissolved state as ions. The ions in the runoff are carried to the streams and rivers to the ocean. Many of the dissolved ions are used by organisms in the ocean and are removed from the water. Others are not used up and are left for long periods of time where their concentrations increase over time. The two ions that are present most often in seawater are are chloride and sodium. the build up of those is what makes the ocean salty...

And why does the percentage of salt found in the ocean water match exactly the percentage of salts in the human body?  Does this occur in other mammals and possibly relies. I would expect that fish's salt percentage would match, they live & breathe thru and in the stuff!