Tourism increases, diversifies and concentrates water consumption in space and time; it contributes to social-ecological processes that often make tourist destinations vulnerable to water stress. Climate change projections foresee an increase in water stress problems in many tourist resorts. Tourist islands are particularly challenged due to their geographical isolation and the limited options for enhancing supply. Despite the significance of the problem, the understanding of the tourism and water–stress complex remains under-researched. In this article, we aim at a novel, integrated and spatiotemporally dynamic conceptualization of tourist islands’ vulnerability to water stress. To do this, we begin by presenting the “Water-Tourism Social-Ecological Systems framework” based on literature on water and tourism, social-ecological systems, adaptation, vulnerability, resilience, and island studies. We then apply this framework to investigate the so far underexplored vulnerability to water stress of the island of Rhodes (Greece). Results from in-depth interviews with key stakeholders along with secondary sources provide insights into the Rhodes Water-Tourism SES dynamics. Our analysis provides an interdisciplinary and multidimensional lens to the water-stress and -tourism complex. It enriches the literature of tourism and water and gives the opportunity to open up the scope of solutions that are being discussed.