Here I will teach you how to make a makeshift water distiller to turn salt water into fresh water.
You will need
2 glass bottles (beer bottles, anything will do)
A metal sheet, tray food container
Some sand
A fire
In some situations where you are by the sea or even by a river, you may need water you do not have readily available.
Ideally the metal tray will act as a heatsink to maintain temperature of the glass.
The two glass bottles should be positioned so the necks are face to face and one bottle suspended above heat. You can support the other bottle using sticks, rocks or whatever you have available.
Firstly, fill the metal tray/sheet with sand, this will allow the head to distribute evenly around the bottle. The other bottle should ideally be covered with sand to act as a heat shield and prevent the bottle shattering from the heat.
The bottles should be positioned properly and pressed into the sand, one above the fire and one acting as a cooler. One bottle should be filled with water to heat up and allow the steam to move to the cooler bottle where it will be turned back into water.
Next we need to wet the sand surrounding the bottle above the fire. Wet the sand on the other bottle and also cover it in a wet cloth, item of clothing or anything that will help to cool it.
The process will begin to work once the sand gets hot enough to distribute the heat to the bottle and evaporate the water inside.
Once the water boils dry in the bottle, carefully remove it, let it cool a little and then add more water and put it back. This will take some time. But after a couple of hours, you will soon have fresh drinking water.
Make sure to test the water before drinking it by having a sip, if it has an unusual taste, it may need another round of distilling to clean it further.
Considering you can nearly always find some bottles, bits of metal and sand, this is pretty good advice!