What type of aquatic unit is XXX?
SM UB-154
SM UB-154' was a German Type UB III submarine or U-boat built for the German Imperial Navy (German: Kaiserliche Marine) during World War I. She was never commissioned into the German Imperial Navy but surrendered to France on 9 March 1919 in accordance with the requirements of the Armistice with Germany and broken up at Brest in July 1921.
German Type UB III submarine