I know this may sound dumb, but make sure the transducer is pointing straight down, and is not mounted upside down! My step dad actually did this and all we saw was "Bottom" which was actually the sky and the surface of the water it was beaming up. To test it stop moving or go very slowly and lower your line and a large lure or weight behind the transducer and you should read something. Other than that just make sure it is as near straight up and down as possible and as deep as the manufacture wants and is not angled as this will distort the image. (consult your manufacturer for their mounting specs.) Hope this helps, heres to marking a ton of fish!