Based at Den Helder, the Royal Netherlands Navy (RNLN) currently operates four Walrus-class boats, all of which were built indigenously by Rotterdamse Droogdok Mij (RDM).  While the Dutch Navy's main area of interest is the Baltic Sea and Mediterranean, the RNLN has also assisted the U.S. Navy in preventing drug trafficking in the Caribbean, where the RNLN holds a minor base on the Netherlands Antilles. 
Submarine Tables for Netherlands
In May 2013, the Netherlands Ministry of Defense signed a contract with Imtech Marine Netherlands to refit the Navy's four Walrus-class submarines, extending their service lives to around 2025.  This extension replaces a previous plan for a mid-life upgrade that may have included fitting the vessels with Air Independent Propulsion (AIP) technology.  Nevertheless, the boats will be provided with enhanced navigation, sonar, and communications systems in order to enhance intelligence-gathering capabilities and adjust to modern operational needs.  This includes their involvement in anti-piracy operations near Somalia, and NATOs 'Operation Active Endeavour' in the Mediterranean, where the Walrus-class is tasked with intelligence-gathering in littoral waters for counter-terrorism purposes. 
In recent years there has been a reduction in Dutch naval assets. The early 1990s saw the Netherlands government decrease its planned procurement of Walrus-class vessels from six to four, decommission two Zwaardvis-class units earlier than initially planned, and decide not to replace them with new Moray-class boats.  More importantly, the Dutch Labor Party has spoken in favor of discontinuing the submarine fleet. Strain placed on the country's defense budget could potentially lead to further cuts. The continued existence of the Dutch submarine fleet is therefore likely to depend on the perceived benefits provided by these boats in the post-Cold War environment or how well they fit into new missions like peacekeeping and the prevention of drug trafficking. 
 International Institute for Strategic Studies, The Military Balance 2009 (London: Routledge, 2009), p. 138.
 Interview with Vice Admiral Clees van Duyvendijk, Commander in Chief RNN, "Navy chiefs of staff on MCM and minelaying," Naval Forces, 2001, Vol. 22, No. 3, pp. 62-68; in ProQuest Information and Learning Company, http://proquest.umi.com; "Chamber of approves deployment of Netherlands troops," NRC Handelsblad, 16 November 2001; in "Netherlands parliament approves troop deployment in Afghanistan," FBIS Document EUP2001111800022.
 Menno Steketee, "Dutch MoD issues contract for Walrus-class submarine life extension," HIS Jane's Navy International, 19 May 2013, www.janes.com.
 "Submarine Forces, Netherlands," Jane's Underwater Warfare Systems, 28 September 2011.
 "Dutch Upgrading Submarines," UPI, 8 December 2011, www.lexisnexis.com; "OSI Geospatial Signs Contract to Provide WECDIS Systems for the Royal Netherlands Navy Walrus Class Submarines," Canada NewsWire, 12 July 2012, www.lexisnexis.com; "Kongsberg Contract for New Passive Sonar Processing Systems to Dutch Submarines," Cision Nordic Companies Press Releases (Scandinavia), 27 June 2011, www.lexisnexis.com.
 "Submarine Forces, Netherlands," Jane's Underwater Warfare Systems, 28 September 2011; "Menno Steketee, "Dutch Submarine to Fight Somali Piracy," Jane's Defence Weekly, 30 June 2010, www.lexisnexis.com.
 Paul Berrill, "RDM profits hit by restructuring," Loyd's List International, 8 June 1991; in Lexis-Nexis Academic Universe, web.lexis-nexis.com.
 "Armed forces will drastically shrink," NRC Handelsblad, 1 July 2003; in "Netherlands minister details defense cuts in letter to parliament," FBIS Document EUP20030702000508; "Defense Ministry Seeks Personnel," De Volkskrant, 17 September 1997; in "Armed Forces 1998 Reorganization, Staffing Needs Outlined" FBIS Document FTS19970917000802.