The single integrated management plan (SIMP) is an umbrella plan for the transnational UNESCO Wadden Sea World Heritage site (DK, DE, NL) and complements the Wadden Sea Plan (2010) which contains the trilaterally agreed targets and policies. With the development of the SIMP, the Trilateral Governmental Cooperation on the protection of the Wadden Sea (TWSC) follows the official request made by the World Heritage Committee in 2014. The plan was developed in an iterative and participatory way in the TWSC including policy and site management levels transnationally. Its purpose is to further facilitate the continuous improvement of transboundary management coordination for the protection and maintenance of the Outstanding Universal Value of the Wadden Sea World Heritage site.