This article explores how water conditions in geographical contexts could influence the construction of teachers’ professional identities and, consequently, their knowledge and beliefs about water sustainability. Water sustainability is defined as the responsible management of water from a perspective that integrates environmental, social and economic sustainability principles. This quantitative study employed an ad hoc questionnaire, inspired by the New Water Culture principles as a conceptual sustainability framework. The instrument, designed with Google Forms, was administered to 221 secondary school teachers from two cities with contrasting water and cultural conditions: Bogotá (Colombia) and Melilla (Spain). Results indicate that teachers’ knowledge and beliefs in both cities are not aligned with water sustainability principles, with no significant differences between the two groups due to their different water conditions. However, there are partial differences related to the respective personal experiences: in Bogotá, teachers show greater concern for water quality, whereas in Melilla the focus is more on the quantity available. These findings underline the importance of promoting teachers’ professional development in water sustainability aligned with professional identities, as a key strategy for nurturing aware and engaged citizens. This approach is fundamental to tackle water stress challenges and foster a paradigm shift towards more responsible, sustainable lifestyles globally.