Its all trial and error. The guys that find them put in weeks of off season work – locating potential spots deep enough on aerials, watching the spring floods and which backwater lakes get rejuvenated, watching the water levels come fall making sure they haven’t dried up, finding public access routes etc etc.
It’s a lot like the guys that put in year round work for hunting- scouting spots, food plot prep and planting, monitoring trail cams, etc.
Pin a few on google maps, hop in the truck with good walking boots and a spud bar and start exploring. Most aren’t willing to put in the work and just try to vulture spots.