 The submarine had a maximum surface speed of 18 @.@ 2 knots ( 33 @.@ 7 km / h ; 20 @.@ 9 mph ) and a maximum submerged speed of 7 @.@ 7 knots ( 14 @.@ 3 km / h ; 8 @.@ 9 mph ) . When submerged , the boat could operate for 65 – 78 nautical miles ( 120 – 144 km ; 75 – 90 mi ) at 4 knots ( 7 @.@ 4 km / h ; 4 @.@ 6 mph ) ; when surfaced , she could travel 10 @,@ 500 nautical miles ( 19 @,@ 400 km ; 12 @,@ 100 mi ) at 10 knots ( 19 km / h ; 12 mph ) . U @-@ 38 was fitted with six 53 @.@ 3 cm ( 21 in ) torpedo tubes ( four fitted at the bow and two at the stern ) , 22 torpedoes , one 10 @.@ 5 cm ( 4 @.@ 13 in ) SK C / 32 naval gun , 180 rounds , and a 3 @.@ 7 cm ( 1 @.@ 5 in ) as well as a 2 cm ( 0 @.@ 79 in ) anti @-@ aircraft gun . The boat had a complement of forty @-@ eight . 
