Seawater is a very abundant source of water, but its high salt content makes it unsuitable as drinking water. However, pure water can be produced from seawater by distillation. This is also known as thermal desalination.
During distillation, the seawater is boiled. The water vapour is then cooled and condensed to form pure water - leaving the salt behind.
The disadvantages of producing drinking water this way include:
Distillation is common in some Middle Eastern countries that have little rainfall, but are wealthy due to their oil reserves.
Another method of desalination is reverse osmosis:
Osmosis is the movement of water across a partially permeable membrane from a region of higher water concentration to a lower water concentration. Reverse osmosis water moves, due to pressure, in the opposite direction.