The Lightship Chesapeake: during WWII, the ship was outfitted with two 20 mm guns

Lightship 116 is one of the last extant lightships in the United has had few modifications during its service. Four generations of lightships were in use in the United States from 1820 to 1983, serving as an essential part of the system of aids to navigation that protected mariners and their ships by marking stations through a combination of light and sound.
Lightship 116 is a well-preserved example from the third generation of lightship design and from the vessel class of Lightship 100, whose most significant advance was the installation of a diesel-electric power plant.