wonkyrig

There are some transducer types and settings that are somewhat conducive to this. Think running on pad at low speed and seeing your 2d screen suddenly cloud up with arches.
 
The more likely scenario is it's a feature of some sort. Channel bend or intersection regardless of depth. Foundation, roadbeds, hard spots, rocks/boulders, brush or cane piles, deep humps, timber. Some lakes have submerged springs. I've found a lot of off the beaten path stuff and areas where fish stack up just due to the way the lake current flows just by idling the channels from main lake all the way to the back, as well as riding around on the trolling motor on 10 livescoping around.
 
The best way to learn it is to devote a section of your fishing time to simply looking around at offshore stuff, and looking at that same stuff in different seasons and conditions. I do think scoping speeds up this process a lot since you can literally follow fish around to get a beat on what they're doing out there.