Learn how to read a fish finder including down imaging, side imaging, and the latest forward facing sonar.

Side imaging fish finders help locate fish and structure while also mapping depth. These are the best we've tested from Humminbird, Garmin, Lowrance, and Simrad.

Side-scan sonar has become more affordable and easier, so more police and sheriff departments now have what are known as "towfish." And they've been using them to rack up some interesting discoveries.

How to Use a Scan Tool There are countless scan tools on the market today. Some are available from major retailers for less than $30, while other, professional-grade offerings can cost thousands.