 The German Imperial Navy ordered UB @-@ 42 from AG Weser of Bremen on 31 July 1915 as one of a series of six UB II boats ( numbered from UB @-@ 42 to UB @-@ 47 ) . UB @-@ 42 was 36 @.@ 90 metres ( 121 ft 1 in ) long and 4 @.@ 37 metres ( 14 ft 4 in ) abeam . She had a single hull with saddle tanks and had a draught of 3 @.@ 75 metres ( 12 ft 4 in ) when surfaced . She displaced 305 tonnes ( 300 long tons ) while submerged but only 272 tonnes ( 268 long tons ) on the surface . 
