The Downscan can display holes, weeds, drop offs, and bars with various sized symbols of fish showing where they are hanging out and at what depth.. and where flat areas are that dont' attract fish the side scanning adds a hundred and fifty dollars to the price and isn't really worth it unless you have a lot of money.so just get the DI/GPS G2 version. the built in maps and GPS are good enough for my trips in the Florida Keys where I need to know how shallow its getting and how far from an Island I am. that makes going out to a particular reef much safer as I loop around and avoid rocky areas of shallows because I can see on the map exactly where I am and fairly good details about the depths.. I bought the SI version and it might someday be worth it to me if I figure out how to ""see"" the obstructions and topography from the side. Interpreting the Downscanning with fish symbols is simple and easy. the side scanning is not so easy. It also has basic maps of lakes in the U.S. though not with depths or details for that you have to buy a SD Card with details of lakes such as the ""Lakes in Minnesota"". $150, but there is a $50 rebate right now.