So I have had my new boat out a few times now and and I can't figure something out. I have a 858cDI and it shows the bottom detail very clear, temperature, depth, GPS, etc all work fine. I have it set with the fish alarm/ fish icon setting and it hasn't shown even one fish. Having never owned a fish/depth finder I don't know if this is common or maybe I need to adjust the sensitivity or something. Any experienced Humminbird owners out there familiar with this problem? Thanks