over time i have built confidence in my sonar and if it doesn't show me fish then they are probably not there, i can see how fish could hide down between big rocks but i don't fish lakes like that, as far as brush go over it with di and it'll show you the fish in the brush, heck sometimes you can count the number of shad in a school. i have found and caught fish i saw on si but it is rare, like was said before everything is so condensed it is hard to see a few crappie on there, mine is a 898 and i run mine at 100' most of the time and have recently went down to 90', i can see and tell if i am in them big time but small scattered fish are hard to tell. i use the si, di and 2d along with my gps to hone in on them rascals, the 898 is the best unit i have ever had and can honestly say it has helped me catch more fish, i only wish i could afford a bigger screen.

fish on the si will appear as a much brighter small white streak, and unless they are right on the bottom should have a shadow and you can roughly tell how high they are in the water column but how far away the shadow is. once fish are found i switch over to 2d to hone in on there exact depth.