You can get very technical about this, but I always go for the easy way. Set the camera in IA mode, lifted the flash, which was set for minus 2/3 intensity, turned off the room lights and allowed the focus assist light to light up the water, which was in a stainless steel sink. Took about 8 shots. This was the best. Some people set up elaborate tanks of water and set up plastic bags of water with a pinhole in them, put their cameras on a tripod etc.