Settings to get best shallow water definition?

I fish lots of sloughs and back waters off of rivers that have no current mapping data and that can be real prop eaters.  I need help figuring out how to set up my Helix 9 to capture the best detail I can get.  IE i would like contours and color displays at 1 foot increments for anything below 15-20 feet.   I played with unit when I first got it and collected some decent data.  was showing good color changes about every 2 feet of depth.  then something got changed on settings and now im losing all my data as its being over written.  cant figure out what got changed.  Any help on specific parameters to set to achieve my end goals would be greatly appreciated.