Think of shining a flashlight at a wall. The light produces a circle of light or cone on the wall. The closer the flashlight is to the wall the smaller in diameter the circle or cone will be. The further away the larger the circle or cone will be. Just like the flashlight your transducer does the same thing underwater. Deeper water=larger cone while shallow water=smaller cone.

Next is determining how close to directly under the transducer the target is. Your unit is color so anything directly under the transducer will show vivid red. As the target gets further away from center the color will turn more yellow. You marked a single fish over a small object like a piece of brush pretty much dead center under your transducer. As you continued you picked up the edge of another part of the brushpile.

The fish on top of that pile was directly under your transducer. You went directly over the brushpile with the transducer but the 3rd fish is on the edge of the brushpile. Brushpile is located at the edge of a very slight drop off. You approached the edge of the drop off from the deeper side first.

If you have old school black and white models never fear. You can still see the same things except you have to interpet the closer to under the transducer as the images that are darker. Don't confuse this with telling hard from soft bottoms based on this criteria.

I say brushpile but at only 3' of water it may be more like a branch with a solid structure like a stump showing under the first two fish.