I was targeting smallmouth bass in the Upper Niagara River and knew that if I located schools of emerald shiners off some of the current breaks the smallmouth would be nearby. Most fishfinders have a tough time marking detail in fast water, but the Raymarine series of fishfinders with CHIRP DownVision marks amazing detail even in the fastest currents!
Look at my screen grab of clouds of small shiners feeding in the main current from the surface down to about 17-feet. I know they are feeding because they are staggered in a large, loose school (not bunched up in a bait-ball). Notice the larger fish below them that I have circled? They are prime targets for hooking-up on deep-diving crankbaits and by jigging!
In this split-screen view that was taken along the shallower structure you can see a sparse school of baitfish near the surface and single smallmouth just behind a rock.
I can tell you from experience that having the most accurate fishfinder helps me catch fish!