Bring the water and sugar to a boil in a large saucepan.
Add the cranberries and bring back to a boil.
Turn the heat down until the mixture is boiling gently. If you let the mixture boil too hard you may end up with a mess on your hands.
Let this boil for about 7 minutes until the sauce begins to gel.
When finished push the mixture through a sieve to strain out the skins. This will produce a sauce must like that in a can, expect with a better, fresher flavor. You can skip this step if you like chunky sauce.