Bill, thanks for the advise on 02 meter, guiding and fishing the Flw walleye tour .... No us pros don't use 02 meters....lol... Growing up I'n eastern Wi, a few of my buds that charter out of algoma and two Rivers don't even have them, there fishing 60- 260 fow... Today's sonar units will show a seasoned person that knows how to read the unit exactly where the termo is at .. Know need for dropping probs down.. Fishing walleyes, the deepest we target fish is I'n the 30-40 ft range I'n lake Erie I'n the dog days of summer. Hence most pro fishing tourneys promote catch and release. Pulling fish from those depths and putting them I'n livewell for a few hours there done for.. Not to mention fish have to be fissed, air bladder of fish goes cabooom pulling fish I'n the 20 plus range .