The composition of salt water, or sea water, is about 35 parts of salts per 1,000 parts of fresh water, though the salinity can vary from between 30 to 37 parts per 1,000. The salts are mostly sodium and chloride, the same ions that go into table salt. Other salts present in sea water include magnesium, potassium and calcium.
Gold is also found in sea water, with about 25 pounds of gold in 1 cubic mile of sea water.
Salinity changes not just the taste but other attributes of water. The saltier the water, the more dense it is. Salt water found in a warm environment, such as the Mediterranean Sea, has a higher salinity than that of bodies of water found in colder climates due to evaporation. Because cold saltwater is more dense than warm, fresh water, it sinks beneath it. This is one of the causes of ocean currents.
The salinity of the oceans and seas is due to the water cycle. When the rain falls, the slight amount of acid in it erodes the rock it falls on, and the salts from these rocks enter the rivers and streams that eventually end up in the ocean. Hydrothermal vents and volcanoes deep in the ocean also lend salt to seawater.