Why is sea water the best liquid conductor of electricity?

Sea water is the best conductor of electricity because it has a high salt content. Salt molecules are made of sodium ions and chlorine ions. When you put salt in water, the water molecules pull the sodium and chlorine ions apart so they are floating freely. These ions are what carry electricity through water.

Pure water is not very conductive, and only a tiny bit of current can move through the water. When salt or sodium chloride (NaCl) is dissolved in it, however, the salt molecules split into two pieces, a sodium ion and a chlorine ion. The sodium ion is missing an electron, which gives it a positive charge. The chlorine ion has an extra electron, giving it a negative charge.