The Oberon class was a direct follow on of the Porpoise-class, with the same dimensions and external design, but updates to equipment and internal fittings, and a higher grade of steel used for fabrication of the pressure hull.

[2] Propulsion machinery consisted of 2 Admiralty Standard Range 16 VMS diesel generators, and two 3,000 shaft horsepower (2,200 kW) electric motors, each driving a 7-foot diameter (2.1 m) 3-bladed propeller at up to 400 rpm.

[2] Opportune was laid down by Scotts Shipbuilding and Engineering Company on 26 October 1962, and launched on 14 February 1964.

[3][4][5] In 1971, Opportune collided with a merchant ship, causing damage to the upper front part of the fin as well as both periscopes.

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