The global commitment to protect 30% of the oceans by 2030 faces several key challenges in preserving nature without exacerbating existing coastal resource conflicts. As ocean protection is rapidly increasing to halt biodiversity loss, we urgently need to understand why people value nature to better address these conflicts. The REVALSEA project will provide a novel theoretical approach and empirical evidence to quantify, predict, and integrate into marine conservation the diverse ways people express why they value their relationship with nature, i.e., relational values, in coastal systems. Relational values (RVs) emerge as a keystone in conservation efforts breaking with the traditional exclusively material valuation of nature and opening a new opportunity to adopt more inclusive and socially relevant strategies for biodiversity conservation. This aspect is rarely explored in marine systems, even when its consideration in conservation is critical to increase equity and reduce resource conflicts. Addressing RVs in marine conservation policies needs overcoming several intergenerational, methodological, and operational challenges. First, it must consider the intergenerational gap between what matters for those who influence decision-making (adults) and for those who have the potential to generate social-ecological changes (youth). Second, it requires the use of innovative interdisciplinary social-ecological research that integrates multidimensional datasets and uses novel machine learning technology to maximise data efficiency while minimising economic costs of data collection and analysis. Finally, it needs transdisciplinary cooperation with stakeholders and decision makers to co-generate specific recommendations for integrating RVs in conservation policies. REVALSEA will focus on the small-scale fisher’s community in Spain as a case study to address all these challenges and develop a cutting-edge and globally scalable approach in other socio-cultural contexts.