 Swordfish had two tubes for 21 @-@ inch ( 530 mm ) torpedoes in her bow . They were stepped vertically and positioned well back from the stem in a notch from the keel to preserve the fine lines of the bow . Two 18 @-@ inch ( 460 mm ) torpedo tubes were positioned on each beam amidships . Each torpedo tube was provided with one reload . Two 3 @-@ inch ( 76 mm ) guns were fitted on the deck in disappearing mounts , one each fore and aft of the conning tower . They were covered by watertight hoods to preserve the streamlining of the submarine . 
