I'm trying to understand one of the most misunderstood and most improperly used tools in fishing and boating; the fishfinder! I've come to the conclusion that, from what I've read on this forum and other sources on the internet, that any unit that has a FishID feature (shows the pretty fishy symbols) should be turned off. I also understand that a fish finder cannot interpret the difference between a fish and other underwater structure (floating or otherwise). My unit (an Eagle Trifinder2) as I understand it, will show fish arches when I turn the FishID feature off. So my question is, if I do turn the FishID feature off and my unit shows arches, how do I know if it's actually marking fish or structure? What makes the difference if it marks a fish symbol or an arch? If you reply, please don't direct me to a link because I've read them all. Thanks!