Most of the lakes around here are shallow (8ft).
Consider your fish finder sends down a cone of ultrasonic waves,
Standard theory says that the cone hits bottom will be 1/3rd the depth
in diameter.
So, say ..... lake is nine feet deep, that would mean that your cone
would only be 3ft in diameter hitting the bottom, and even less as it
travels up in the water column = pretty much useless, fun to watch but .......
Most of these guys just use jigs, tube/grub/roadrunners, and a few do use minnows
and minnow tipped jigs.
Ha ! ! Ain't no deep holes around here that I know of (some deeper lakes are found in
Kissimmee area)......
As far as depth, set different poles at different depths till ya find em, still you'll find em
a foot deep to four/five foot etc, etc, etc .... Just gotta experiment with that..
More better info from the rest of these guys ......