Boathouses were once a staple of lake homes. Current shoreline zoning regulations have led to the decline of this type of structure, with only older boathouses dotting the shorelines of our lakes.
Here’s a Humminbird Side Imaging look inside a boathouse. As you can see, the water in the boathouse extends quite a ways back…farther back than the original shoreline. This particular boathouse has 3 bays, and a boat is present in the middle bay. The lower unit of its motor is the bright white return in the center of the middle bay, with the sonar shadow from the lower unit preventing us from seeing the water between the lower unit and the back of the boathouse.