The Porpoise class was the first class of operational submarines built for the Royal Navy after the end of the Second World War, and were designed to take advantage of experience gained by studying German Type XXI U-boats and British wartime experiments with the submarine, which was modified by streamlining and fitting a bigger battery.
The Porpoise-class submarines were 290inchesft3inchesin (ftin) long overall and 241inchesft0inchesin (ftin) between perpendiculars, with a beam of 26feet and a draught of 18inchesft3inchesin (ftin). Displacement was 1565LT standard and 1975LT full load surfaced and 2303LT submerged. Propulsion machinery consisted of two Admiralty Standard Range diesel generators rated at a total of 3680bhp, which could charge the submarine's batteries or directly drive the electric motors. These were rated at 6000shp, and drove two shafts, giving a speed of 12kn on the surface and 16kn submerged. Eight 21adj=onNaNadj=on torpedo tubes were fitted; six in the bow, and two in the stern. Up to 30 torpedoes could be carried, with the initial outfit consisting of the unguided Mark 8 and the homing Mark 20 torpedoes.
Cachalot attended the 1977 Silver Jubilee Fleet Review off Spithead when she was part of the Submarine Flotilla.[1]
She was sold on 12 November 1979 for breaking up at Blyth.