Believe it or not, drinking more water will help with water retention. By drinking more water it helps to balance out the electrolytes in your body (sodium and potassium) and after a few days you will definitely notice the difference. The RDA for water is 2.5 liters per day, try to double that, in cups it is about 20. I know it is a lot and you'll be in the bathroom every 15 minutes but it will make a difference after a week or so. Just keep a bottle with you and sip at it all day. Keep rubber bands around it to show how many you have finished. When you are done a bottle, remove a band. Give it a try.