I'm mostly a fly fisherman, so I don't know a whole lot about electronics, but a few years ago I purchased a very inexpensive, hand-held fish finder --   (You need to Login or Register It sells for $50 on Amazon. This is a very basic sonar, but it works surprisingly well. We used it to find the lakers in QP with great success! It comes with an adapter that allows the transducer to screw onto a threaded broomstick. I just bring along a short piece of broomstick with the threads and improvise a mount to a thwart using duct tape.

This is my very first post here. Hope I did it right.   :)