Water and fat are two different things. You can hold tons of water and still lose lots of fat.
Some guys hold more water in gh than others. Some only hold it in the muscle while for others, it goes everywhere. Over time, you'll get used to it and some of the fluid retention will reduce. Your best bet is to start the dose low and slowly build over weeks. When and if you reach a point that the water is too much, stop increasing until you adjust. Then when you are comfortable again, increase a little more. I'd start with 2iu. Then give it a few wks and see what happens. Then when you want to increase, increase by .5iu