Garmin has combined its excellent sonar technology with a mapping GPS unit that gives you several options.  This unit can operate in either GPS or sonar mode or in a split screen mode that gives you both features.

I particularly like the instant marki9ng feature on the GPS.  Other units require several inputs to log a particular waypoint occurrence.  The 168 logs a waypoint with a single button push, so that when you mark fish or structure on the bottom, it's easy to keep that spot!

The unit is somewhat small, and operates in black and white gray scale.  The contrasting ability and backlighting make it easier to read in sunny conditions, but the three inch display screen could be a little larger.

The built-in world wide mapping ability is enhanced by downloading from Garmin's Mapsource CDROMs.

I personally prefer a color bottom machine for finding fish, but overall this is a fine entry level step to the upper strata of GPS/Sounder combo units.