 SM UB @-@ 42 was commissioned into the German Imperial Navy on 23 March 1916 under the command of Kapitänleutnant Fritz Wernicke . UB @-@ 42 , Wernicke 's first U @-@ boat command , was assigned to the Navy 's Pola Flotilla ( German : Deutsche U @-@ Halbflotille Pola ) . Although the flotilla was based in Pola , the site of the main Austro @-@ Hungarian Navy base , boats of the flotilla operated out of the Austro @-@ Hungarian base at Cattaro which was located farther south and closer to the Mediterranean . German U @-@ boats typically returned to Pola only for repairs . The first months of service for UB @-@ 42 proved unsuccessful ; the U @-@ boat sank no ships while in the Pola Flotilla . 
