I'm very new to underwater imaging, but have a desire to locate objects in a nearby lake. The lake has an average depth of 20' and I was considering building a side scan sonar type system to tow behind a boat once the ice melts. Can someone point me in the right direction? I'm not interested in a $10k professional setup, I'm looking for the best, but inexpensive, way to find things in the bottom of a shallow lake. Where do I start?