I had real trouble tuning the DI on my HB999 also. One issue was that anytime I got in water more than 15' deep the image became pretty much unusable. No amount of adjustment would help it. One of the guys on this forum suggested that I switch the DI to Narrow Beam(options are Narrow, Medium, Wide) and the difference was amazing. Now my images are very clean and getting better as I continue to master the Hb999.