 Swordfish had two Parsons geared impulse @-@ reaction steam turbine sets , each driving one of the two propeller shafts . The turbines were powered by a single Yarrow @-@ type boiler . They were designed to produce a total of 4 @,@ 000 shaft horsepower ( 3 @,@ 000 kW ) at a working pressure of 250 psi ( 1 @,@ 700 kPa ; 18 kgf / cm2 ) which used a superheater to increase the working temperature by 100 ° F ( 38 ° C ) . She was fitted with two electric motors which had a combined output of 1 @,@ 400 bhp ( 1 @,@ 000 kW ) . Two battery rooms each had 64 battery cells . It is uncertain if the ship reached her designed speed of 18 knots on the surface , although it seems unlikely given her increased displacement over Laurenti 's original design . Maximum speed was 10 knots ( 19 km / h ; 12 mph ) underwater . 
