I’ve been running the navionics chip for the past year or so in my 332c. I think it provides a good general idea about depths. There are still some places where the map data would have me believe that I’m running over dry land (which I tend to avoid) but for the most part I’m happy with it.
Can’t wait for some one to come out, collect a new set of data and publish map data with 1 ft contours! Likely won’t happen, given the ever-changing nature of the riverine environment.