Her keel was laid down on 1 August 1955 by Scotts Shipbuilding and Engineering Company at Greenock.

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 Seraph, which was modified by streamlining and fitting a bigger battery.

[2] Propulsion machinery consisted of two Admiralty Standard Range diesel generators rated at a total of 3,680 brake horsepower (2,740 kW), which could charge the submarine's batteries or directly drive the electric motors.

These were rated at 6,000 shaft horsepower (4,500 kW), and drove two shafts, giving a speed of 12 knots (14 mph; 22 km/h) on the surface and 16 knots (18 mph; 30 km/h) submerged.

[2] Cachalot attended the 1977 Silver Jubilee Fleet Review off Spithead when she was part of the Submarine Flotilla.