Sustainability sells. Like in many other sectors, in tourism the demand for products and services from environmentally and socially sound tourism providers is increasing steadily (Center for Responsible Travel 2015). There are several ways how sustainable practices can be incorporated in the management of tour operators, tourism businesses and destinations. Eco-labels are considered to be one of them (Esparon, Gyuri & Stoeckl, 2014). Reliable eco-labels and other certification schemes encourage tourism professionals to assess the performance of their businesses or destinations on the base of pre-set sustainability standards and to make improvements where necessary. For tourists, certifications in the form of visual labels are helpful indicators to find tourism providers that place high emphasis on responsible practices (Aloisi de Larderel, 2000). One of the oldest and most successful tourism certification schemes is the Blue Flag programme (Font & Mihalič 2002). The Blue Flag is an international, voluntary eco-label for beaches, marinas and since 2016 also for sustainable boating tourism operators, which has been implemented in 49 countries worldwide. The new certification for boat-based tourism activities is the first of its kind, focusing on a branch in tourism which has a high impact on marine and freshwater environments (Warnken & Brynes 2004).