As a Colorado Persian cat breeder, we state on our Persian Grooming information page, NEVER, NEVER, NEVER, EVER put a matted cat into water.  Water will make the mats tighter and it is not likely that you get the mats out without shaving your cats coat off. 

Dematting tools range from tools that cut the coat off, scissors to combs and brushes.  We prefer a wide metal tooth comb for dematting.  The wide metal tooth comb works well in separating the hairs and detangling.

If your cat is extremely matted, rather than pulling on the coat, or trying to cut at the matting, it might be better for both you and your Persian cat to "throw in the towel" and call in a professional groomer.  Your local groomer can give a couple of different cuts that look cute.  Depending upon where the mats are located on your cat, a lion cut might be more suited for a cat that is matted all over.  The lion cut is just as it sounds, when completed it is similar to what a lion would look like.  The hair is left in place on the head and neck, tip of the tail and legs then the rest of the cat is shaved short.  If your Persian cat has mats basically on the stomache and in the armpits, a line cut might be the better option.  A line cut is a cut where the hair located on the stomache area is cut off in a line on the underside of the cat.

Unless you are a groomer by profession, we never recommend taking a pair of scissors to an animals coat.  When you are attempting to trim out a mat your cat could move ever so slightly and you can have an emergency on your hands.  The skin of your cat is very thin and can cut very easily with a pair of scissors.