Garmin's GPSMAP 172C (and not garman gps, as some say) with Internal Antenna, has features such as:
Wide Area Augmentation System-enabled (WAAS), 12 channel (parallel) GPS receiver,
Sunlight-readable CSTN with adjustable CCFL backlight ,
Internal, worldwide marine basemap ,
Accepts standard Garmin data cards; single, front-loading slot ,
Internal memory backup for user settings in case of loss of power,
2 NMEA serial ports,
Stores up to 3,000 user waypoints, 50 reversible routes (50 waypoints per route) ,
Water-resistant to IEC 60529 IPX7 standards (submersible in 1 meter of water for 30 minutes) ,
Compatible with Garmin's GSD-20 for sounder capabilities,
Display size: 4.5" diagonal, 3.2"W x 3.2"H, 320x320 pixels,
Unit dimensions: 6.3"W x 4.9"H x3.7"D.

This GPS receiver accepts MapSource® BlueChart® offshore marine cartography that features detailed depth contours, inter-tidal zones, wrecks, navaids, and other points of interest. For smaller water anglers, the Garmin 172C is compatible with MapSource Recreat. Lakes with fishing spots, having fishing areas, boat ramps, marinas, and hazards for hundreds of popular lakes, including Canadian lakes. Data cards can be inserted into the slot on the front of the 172c and this device can be upgraded to a combination chartplotter/sounder by adding a Garmin GSD 20 sonar and transducer.

Top of this page for info on the Garmin gpsmap 172c