<p>India’s marine biodiversity remains unevenly documented, with fragmented and inconsistently accessible observations limiting their use for long-term assessment and conservation planning. To address this gap, we developed OceanEyes, a citizen-science mobile application designed for standardised, high-resolution documentation of marine biodiversity across India’s EEZ. The platform integrates Darwin Core-compliant data structures with a two-tier expert validation system, ensuring scientific accuracy and interoperability with global repositories. Unlike existing platforms, OceanEyes is specifically tailored to marine ecosystems, incorporating domain-specific metadata (e.g., habitat, depth, substrate) and enabling offline data collection in low-connectivity coastal regions. A comparative analysis demonstrates that OceanEyes bridges the gap between global generalist platforms and region-specific applications by combining marine focus, standardisation, expert validation, and integration with OBIS via IndOBIS through standardised data export. Initial deployment (November 2023–March 2026) recorded 539 users, with ~ 74% from India, and peak engagement of 232 active users, stabilising at 60–100 users, indicating sustained participation. These results demonstrate the platform’s usability and scalability for participatory marine monitoring. By combining citizen participation with rigorous quality control and FAIR-compliant data workflows, OceanEyes provides a scalable and scientifically robust framework for marine biodiversity documentation, with direct relevance to marine spatial planning and national commitments under the Convention on Biological Diversity and SDG 14.</p>