My fishing partner has been bugging me to pick up a more advance fishfinder, something with a gps so we can map out our spots (instead of trying to find them by looking at shore landmarks!). Having said that, I am NOT a guy who is good with technology. I use a map when driving, I don't know how to text, and I don't download this from that site and put it on this chip and stick it in that hole...In other words, something user friendly, where I can mark off spots I want, and also see what's coming up (I was with a friend once, and he had a map on his finder, he could see that we were about to come up on a shallow shelf). I think his finder had a puck or thru-hull transducer. Are these compatible with an aluminum hull or only fibreglass? He may be willing to sell it to me. If not, is it realistic to get a decent unit for $500? Any recommendations?