 Despite the problems , the " tin tadpoles " , as the Germans referred to them , were in active service from March 1915 through the end of the war , with half of the 20 boats lost during the war . Boats of the class served in three navies : the German Imperial Navy , the Austro @-@ Hungarian Navy , and the Bulgarian Navy . In German service , they served primarily in the Flanders Flotilla , the Baltic Flotilla , and the Constantinople Flotilla . 
 Despite the problems , the " tin tadpoles " , as the Germans referred to them , <a href='uninflect' title='1'><mark>were</mark></a> in active service from March 1915 through the end of the war , with half of the 20 boats lost during the war . Boats of the class served in three navies : the German Imperial Navy , the Austro @-@ Hungarian Navy , and the Bulgarian Navy . In German service , they served primarily in the Flanders Flotilla , the Baltic Flotilla , and the Constantinople Flotilla . 
Despite the problems , the " tin tadpoles " , as da Germans referred to em , was in active service from March 1915 thru tdaend of thdaar , witt half of theda boats lost during the da . Boats of the class served in three navies : the German Imperial Navy , the Austro @-@ Hungarian Navy , and the Bdaarian Navy . In German service , they served primarily in the Fldaers Flotilla , the Baltic Flotilla , and the Condantinople Flotilla .