hi wondered if any of you guys can help, I have a garmin 551s and im sure im not interpreting info and colour on screen , ii have tried fishing ,catching nothing and getting cheesed off , for a novice on garmin colour plotters what do the colours of sea bed determine and should sonar settings be in auto mode? ,any help would be much appreciated all in novice wording lol thanks in advance for any help , the manuals you get with them do not help at all