Been using one for three seasons now on my bow. Would never want to fish without it now that I’ve experienced the numerous benefits. What he said is probably true, but so much more information is provided by the unit as well. Think side imaging, but in all directions – and the boat doesn’t have to be moving! Here’s a real life example of what the unit will do for you…was fishing a weed line in 15′ of water for walleyes, saw three large boulders at my 2 o’clock position about 60′ out, that I didn’t know existed, with what looked like a fish or two on them. Pitched out to where the boulders were and – no surprise – a 24″ walleye immediately ate my Jigging Rap. Happens all the time and for every species we pursue. As for 80-90′ depths, I don’t know how well the unit would operate since I don’t fish that deep. I can tell you from firsthand experience the unit will pick-up schools of ciscoes in 40 – 50′ though.