The ship's portlight, sometimes called porthole or bull's eye, is a round or oval window in a ship's hull or superstructure.
Portlights are used primarily to provide natural illumination. They are found on all vessel types: passenger, Ro-Ro and container ships, tugboats, barges, etc.
Ship's portlights are made of a pane of safety glass in a round or oval frame. Some can be opened by unscrewing wing nuts and swinging the threaded shaft out of the way. Other models are fixed. Some include a hinged, opaque cover.
Choice will depend on design and dimensions. Distance from the waterline will determine whether the portlight will be fixed or opening.
