Most important to first understand how to get a quality image, then how to intrepret that image.
1) Match boat speed and chart speed.
2) SI distance 3x the depth. (Easy rule to break when you start to understand how to intrepret images)
3) Adjust Sensitivities, Sharpness, Contrast for the optimum level of clutter you want.
4) First time on the water, go by known structures i.e. docks, boat landing, fallen trees, vegitation, etc…KNOWING what you are looking at will help you understand the image shown.
5) Flashlight theory. Imagine your SI as a flashlight. Flashlights cast shadows behind objects…So does SI. The harder the object or closer the object the brighter it will be. The further, the darker. This helps determining when the bottom contour is getting deeper or shallower, or you’ve found a ledge/tree/etc. It’s all about understanding shadows.
One thing i should add, before you start posting screencaptures online, first remove the GPS coordinates from your readouts Might save a few hotspots :0