 20 Type UB I submarines were built , 17 for the German Imperial Navy and three for the Austro @-@ Hungarian Navy . Two of the German submarines — UB @-@ 1 and UB @-@ 15 — were sold to Austria @-@ Hungary and commissioned into the Austro @-@ Hungarian Navy as U @-@ 10 and U @-@ 11 , respectively . Those two and a further three built by AG Weser comprised the virtually identical U @-@ 10 class for the Austro @-@ Hungarian Navy . Another of the German submarines , UB @-@ 8 , was sold to Bulgaria in May 1916 , becoming Podvodnik No. 18 . 
 20 Type UB I submarines <a href='uninflect' title='1'><mark>were</mark></a> built , 17 for the German Imperial Navy and three for the Austro @-@ Hungarian Navy . Two of the German submarines — UB @-@ 1 and UB @-@ 15 — <a href='uninflect' title='2'><mark>were</mark></a> sold to Austria @-@ Hungary and commissioned into the Austro @-@ Hungarian Navy as U @-@ 10 and U @-@ 11 , respectively . Those two and a further three built by AG Weser comprised the virtually identical U @-@ 10 class for the Austro @-@ Hungarian Navy . Another of the German submarines , UB @-@ 8 , was sold to Bulgaria in May 1916 , becoming Podvodnik No. 18 . 
20 Type UB I submarines was built , 17 for da German Imperial Navy and three fa tdaAustro @-@ Hungarian Navy . Two of thdaerman submarines — UB @-@ 1 and UB @-@ 15 — was sold to Austria @-@ Hungary and commissioned into the Austro @-@ Hungarian Navy as U @-@ 10 and U @-@ 11 , respectively . Those two and a further three built by AG Weser comprised thedartually identical U @-@ 10 class ffathe Austro @-@ Hungarian Navy . Another of the German submarines , UB @-@ 8 , was sold to Bulgaria in May 1916 , becoming Podvodnik No. 18 .