Your side and down images both will always be distorted if you are sitting still. A fish, a tree branch, or anything else that you mark will just show as a solid line if your boat is not moving. Now at times it will look different if you are sitting still and a fish swims through the area covered by your transducer beam.

On the bow of my boat I use a Garmin Livescope. It uses a different technology than side or down imaging. With Livescope you don't need to be moving to get clear images of fish and brush.