Symbioter brings together key actors from across the BSR to unlock the potential of water and nutrient reuse, accelerating the shift towards a circular, climate-resilient water economy. The region faces growing pressures from water scarcity, nutrient losses, and climate change, while many valuable EU project results remain fragmented and underused locally. Symbioter integrates and applies these achievements to create local water symbioses – practical collaborations between municipalities, utilities, businesses, and interest groups to recycle, recover, and reuse water and nutrients with the help of nature-based solutions and diverse treatment technologies. The platform will synthesize best practices and digital tools from Interreg and Horizon projects, delivering targeted capacity-building for local authorities, public service providers, and networks of water stakeholders across the BSR. Symbioter shows how small-scale cooperation can deliver measurable environmental benefits, reduce eutrophication, and increase water resilience. Through mentoring, training, and transnational exchange, the project will help stakeholders apply tested solutions in daily practice, develop local microsymbiosis concepts, and support the EU environmental policies. The platform employs multiple and innovative approaches to knowledge exchange and capacity building, ensuring the optimal impact of Symbioter in empowering local water stakeholders in the Baltic Sea Region.