We know you don't have extra space on your boat, so we packed a ton of features into this combination chartplotter/sounder unit. The GPSMAP 238 is a dual-frequency sounder that features exceptional resolution, a fast redraw rate, and split-screen capability so you can view your position and sounder information at the same time. This unit is WAAS capable for greater accuracy, and it has a built-in worldwide basemap with coastline detail, U.S. tide data, and inland features. The GPSMAP 238 also accepts optional data cards with GARMIN's BlueChart™ marine cartography for additional detail, and is fully compatible with many of our MapSource™ CD-ROM products.