 U @-@ 20 was an ocean @-@ going submarine that displaced 173 tonnes ( 191 short tons ) surfaced and 210 tonnes ( 231 short tons ) submerged and was designed for a complement of 18 . She was 127 feet 2 inches ( 38 @.@ 76 m ) long with a beam of 13 feet ( 4 @.@ 0 m ) and a draft of 9 feet ( 2 @.@ 7 m ) . For propulsion , she featured a single propeller shaft , a single 450 bhp ( 340 kW ) diesel engine for surface running , and a single 160 shp ( 120 kW ) electric motor for submerged travel . She was capable of 12 knots ( 22 km / h ) while surfaced and 9 knots ( 17 km / h ) while submerged . Although there is no specific notation of a range for U @-@ 20 , the Havmanden class , upon which the U @-@ 20 class was based , had a range of 1 @,@ 400 nautical miles ( 2 @,@ 600 km ) at 10 knots ( 19 km / h ) , surfaced , and 23 nautical miles ( 43 km ) at 8 knots ( 15 km / h ) submerged . 
