I would probably use this device for locating Walleye but mostly its about Lakers.  There's a lot of trout in WCPP which has become my haunt.  Last summer I caught quite a few 6 pounders so I can't complain.  But it all seemed pretty hit and miss.  I'd figure, it's summer so they must be down 60 feet or so.  So that's a guess.  Then I'd tie on a 3 oz weight figuring that would get me down there.  And that's another couple of guesses.  But if I know that Lakers like the water between 48 and 53 degrees and I can locate those temps.  And if I can determine where my baits are then I've put myself in a position to catch some fish based on something more than hunches and dumb luck.  Although truth be told, in most of the lakes in WCPP, the fish are so dumb that hunches and luck seem to be enough (evidently, because I'm catching fish.)