Bring the water and sugar to a boil in a saucepan.
Add the cranberries and bring the water and sugar back to a boil. Let it boil for about 1 minute then turn the heat down till your berries are simmering. Stir continuously.
Continue to stir as you simmer the berries for about 10 minutes. The sauce is done when the sauce has become thick enough to heavily coat a spoon without dripping. The sauce will continue to thicken as it cools.
Refrigerate overnight, or at least several hours before serving.
Notes
Tips for additional flavors
Instead of water, use a 100% fruit juice. Orange juice and orange zest is commonly used. Apple juice, raspberry juice, pomegranate juice, cherry juice, grape juice are all worth trying if you like the flavor of them. When a juice is added to the sugar instead of water the sauce gets a little sweeter. Pleasantly sweeter in my opinion. And here is a flavor twist for you. It may be contrary to your intuition, but a nice aged vinegar, especially balsamic vinegars really bring a richness to your cranberry sauce. It intensifies the sweetness.