Use the navigation bar in the upper left corner of the map to zoom in and zoom out on Lake Maria. You can see satellite images of Lake Maria by clicking on "Satellite" or "Hybrid" in the upper right corner of the map.
Use your mouse to get GPS coordinates for any spot on Lake Maria. Simply click and drag the red arrow to the spot you are interested in and the geocodes (latitude + longitude) will appear in the boxes above - it's that easy!