SM UC-99 was a German Type UC III minelaying submarine or U-boat in the German Imperial Navy (German: Kaiserliche Marine) during World War I.
A Type UC III submarine, UC-99 had a displacement of 491t when at the surface and 571t while submerged. She had a length overall of 56.51m (185.4feet), a beam of 5.54m (18.18feet), and a draught of 3.77m (12.37feet). The submarine was powered by two six-cylinder four-stroke diesel engines each producing 300PS (a total of 600PS), two electric motors producing 770PS, and two propeller shafts. She had a dive time of 15 seconds and was capable of operating at a depth of .
The submarine was designed for a maximum surface speed of and a submerged speed of . When submerged, she could operate for at ; when surfaced, she could travel at . UC-99 was fitted with six mine tubes, fourteen UC 200 mines, three torpedo tubes (one on the stern and two on the bow), seven torpedoes, and one 10.5sp=usNaNsp=us SK L/45 or 8.8sp=usNaNsp=us Uk L/30 deck gun . Her complement was twenty-six crew members.
The U-boat was ordered on 12 January 1916 and was launched on 17 March 1918. She was commissioned into the German Imperial Navy on 20 September 1918 as SM UC-99.[1] As with the rest of the completed UC III boats, UC-99 conducted no war patrols and sank no ships. She was surrendered to Japan on 22 November 1918. The U-boat was renamed O-5 for Japanese service from 1920 to 1921. O-5 was dismantled at the Yokosuka Navy Yard between March and June 1921. The hulk of O-5 was disposed of as a gunnery and torpedo target in October that same year.[2]