This case study report presents the outcomes of a co-design process focused on sustainable water management amidst rising demand driven by tourism on the Adriatic Coast, with a specific focus on Krk Island. Under the umbrella term “Water-Tourism-Nexus”, the regulate project team together with engaged stakeholders from water management, tourism, government, and science developed integrated strategies ensuring water security for residents and tourists while preserving the island’s environment and economy. Research activities and a workshop series guided the formulation of site-specific measures that could be implemented on Krk Island. Supply-side measures include water conservation, water reuse and desalinization and seawater pools. Demand-side measures involve spatial planning, mitigating uncontrolled tourism and new water fee structures. Based on our shared experience, we emphasize continuous stakeholder collaboration, supportive policy frameworks, financial incentives and public awareness campaigns as core components of a sustainable water future on Krk Island. The report should ideally serve as a blueprint for sustainable water management beyond Krk Island, highlighting the necessity of stakeholder-driven approaches and integrated solutions in balancing human wellbeing and economic growth with environmental preservation.