Originally Posted by Andy Moore
Correct. The proper way to use a fishfinder is with 'fish arches' turned on.
Quite right - you get a very different return from the swim bladder of a fish that you do from general muck and crud that is floating under the transom. This is what gives rise to the arches. I know its always difficult but try trolling round somewhere known to have a high fish density (e.g. round the base of an old pier - just watch out for divers though
). Switching to arches mode should give you a fine set of returns. If it doesn't then let us know your settings and we can all take it from there