No matter the depth, sonar is a must even if only to find small fish in the area. I was out yesterday in the middle of the lake traveling to my next spot and there it was: a school of fish in the middle of no where in 10'. Stopped the boat, cast my jig and caught a few. There were fish in shallow water first indicated by fish in deeper nearby water indicated fish vis sonar. Sure enough, I hit a school of panfish and caught 2 doz.

The unit doesn't have to be fancy. It just needs to show bottom hardness, bottom weeds if any and any fish in the water column.

When it comes to fishing is zero structure water, a buoy float makes sense to be able to stay and cast where the fish are. A wind will take the boat and the fish are lost.