HMS Otter (S15)
HMS "Otter" (S15) was an submarine of the Royal Navy. Design and construction. 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. As designed for British service, the "Oberon"-class submarines were in length between perpendiculars and in length overall, with a beam of , and a draught of . Displacement was 1,610 tons standard, 2,030 tons full load when surfaced, and 2,410 tons full load when submerged. Propulsion machinery consisted  of 2 Admiralty Standard Range 16 VMS diesel generators, and two electric motors, each driving a 3-bladed propeller at up to 400 rpm. Top speed was when submerged, and on the surface. Eight diameter torpedo tubes were fitted (six facing forward, two aft), with a total payload of 24 torpedoes. The boats were fitted with Type 186 and Type 187 sonars, and an I-band surface search radar. The standard complement was 68: 6 officers, 62 sailors. "Otter" was laid down by Scotts Shipbuilding and Engineering Company on 14 January 1960, and launched on 15 May 1961. The boat  was commissioned into the Royal Navy on 20 August 1962. The only Oberon class submarine fitted with a mild steel casing needed when deployed as target for practice torpedo attacks. Decommissioning and fate. "Otter" was paid off on 31 July 1991.