The German Imperial Navy ordered its first fifteen Type UB I boats on 15 October 1914 . Eight boats — numbered UB @-@ 1 to UB @-@ 8 — were ordered from Germaniawerft of Kiel , and seven boats — numbered UB @-@ 9 to U @-@ 15 — from AG Weser of Bremen . After two of the class , UB @-@ 1 and UB @-@ 15 , were sold in February 1915 to ally Austria @-@ Hungary ( becoming U @-@ 10 and U @-@ 11 in the Austro @-@ Hungarian Navy ) , the German Imperial Navy ordered UB @-@ 16 and UB @-@ 17 from Weser . A further three for Austria @-@ Hungary — U @-@ 15 , U @-@ 16 , and U @-@ 17 — had been ordered from Weser by April , bringing the total number constructed to 20 .