First of all - are you using any ancillaries with your deca? If not, you should be using an AI to control estrogen levels (which can perfectly cause water retention), and cabergoline for prolactin control (which can also increase water retention). If you are not using those drugs at this moment, you should start taking them ASAP, and things will get well really fast. If you are already using them, then you either need to reconsider your dosage, or make sure that you are using the real ones.