Became the most successful Dutch submarine during the Second World War. Originally to be named K XXI. Sister ships O22-27. Design of the Royal Netherlands Navy. Supervisor during building was naval chief engineer G. de Rooij. Contract signed on 10/19 June 1937, ordered on 12 April 1937, to be delivered on 10 December 1939, 580 ton steel no. 52 à 203,65 per ton ordered on 3 February 1937, laid down in shed II on the island shipyard of the Kon. Mij. De Schelde, Vlissingen, Netherlands with yard number 207 on 13 July 1938, machinery placed between 8 May-28 September 1939, launched by Mrs. M.W. Kwak-Bout on at 13.15 o’clock 21 October 1939, docked 9-27 December 1939 and 10-12 April 1940, trials while berthed 30 November and 1 December 1939, technical trial 9 January-10 March 1940, torpedo testing off Den Helder, Netherlands 5-20 March 1940, delivered on 12 May 1940, left 12 May 1940 the locks at Vlissingen bound for England under own power, there finished at Rosyth, Scotland and ready on 22 June 1940, de commissioned on 2 November 1957 and sold to the firm G.P. van Beckum, Alkmaar, Netherlands to be broken up on 24 January 1958.
Dimensions 77,70 (over all) x 6,20-6,55 x 5.851 (hold at thrush no. 70) x 3,940 metres. Draught at launching with a displacement of 836 tons was 3,01 (fore)-3,63 (aft) metres. Displacement 974/990 (surfaced)-1.186/1.208,5 (submerged ) tons. Standard displacement 889,47 tons. Speed 19,5 (surfaced)-9 (submerged) knots. Three screws. Two-7 cylinder Sulzer Diesel engines supplying at 450 rpm totally 5.300 ahp. 70% was welded instead of riveted.
