idiots guide to electronics (I need one)

When I had the money to buy electronics, I had no urge to do so. Now that I have no money I have the urge to try some out. So......a few questions persist. I don\'t have a motorized fishing boat with lots of room. I do have a kayak and a canoe. I have looked at hand held depth finders in the past, but was unsure of what to look for. I still spend LOTS of my time shore fishing or wading. I was hoping to take the canoe out to some of my frequently used spots and make a \"topo\" with a depth finder for reference and to see where the fish tend to hold. And for the obvious reasons it would be nice for new waters. So, what is out there? I guess it would have to be able to run on its own battery, be fairly small, mark depth and show fish/structure. I guess most nowadays have GPS or Lowrance, but for now that is unneccesary. If anyone can think of an older model, or last year\'s model that I could find on the cheap let me know where to look. If I had a good lead on a design/model then I could search ebay or craig\'s list and see what pops up. What price range is reasonable and at what price does the quality fo the unit tend to drop off considerably? In the boundary waters years ago when I went on my first ice out lake trout fishing trip I went solo on a lake I had not fished before. I did find some shallow trout and found shallow pike for flyfishing, but for the main body of the lake I took a one hundred foot rope and marked it off every foot with black sharpie, and I think every ten feet with red sharpie. I had a stuff sack with a rock and lowered it over untill I hit bottom. I would mark the depth by counting red and black marks. Worked pretty slick for some time, but really was time intensive for mapping out and sizeable area, and looking for the magic drop offs and features a real pain in the rump.