One of the top products among GPS fishfinder combos is the Garmin echoMAP 50s. On its 5 inch display that gives crystal clear images in both day and night you can view your navigation data and target fish.
Most GPS fishfinders are combo units, meaning they have both a depth sounder as well as a chartplotter. A chartplotter will showcase your location, superimposed over a map. This allows you to know your exact location at all times. Entering waypoints is as easy as pushing a button with these units, and this priceless function will allow you to mark fish, structure, launch ramps, or anything else you desire. Once saved, that information can be selected at any time, and those spots can be revisited, or avoided, during future visits. (This is an awesome feature for returning to that honey hole of a mid-lake hump!)