Stem and coarsely chop the apples. Include the seeds, skins and core. Cover with the water and bring to a boil, reduce to a simmer, and cook, partly covered for 45 minutes. Strain through a damp cheesecloth. Keeps best if frozen. I usually put it in a plastic tub and chip off what I need, but ice cube trays are ideal. This is a concentrated (natural) pectin source. You can use it for jellies or jams, when the fruit has little pectin of its own (such as blueberries or strawberries.) Be sure to try to find unsprayed apples if at all possible. This stuff really does work.