You will have to get the Blue Chart add-on around $100 for complete details: depth, obstructions and other items (ocean). Without Blue Chart, you get the ocean/land outlines without any other details except for your tracks and waypoints. I live in Ventura CA which has a great bay with Islands. The bay and Islands show up without Blue Chart. There are several lakes near me but are not included in the Blue Chart. I would have to purchase a "land" edition for the lakes. I've sailed around the lake with the GPS on and have an outline of it now for my map. I downloaded this into the Blue Chart and keep it for reference for the lakes. I also tow/launch/recover my M15 with a Pontiac Grand Prix V6. I don't have any problems. My car is rated for 1,200#. I'll put a trans cooler on it before I go any long distance. Norm M15 #172