No, the snapshot is just an image of the history shown on the screen. Even if the image were georeferenced and the boat speed was consistent and you made no turns, the waypoint just would not be as accurate. Every ping has GPS data, speed, heading, etc associated with it, you would have to store all this info in each line of the image file as well to mark the waypoint and it would just be too big in the end.
The snapshot is nothing more than a screencapture!
Robert