<ul data-eligibleForWebStory="true">The Marine Organizational Body Size (MOBS) database is a new open-access resource with body size data for over 85,000 marine animal species.MOBS covers 40% of all described marine animal species and aims to achieve 75% coverage.The database enables research on the ocean's biodiversity and global ecosystem.Body size data is essential for understanding evolution, ecology, and behavior of marine animals.MOBS focuses on body length, as it is commonly documented unlike body mass.Data collection and updates are facilitated by the World Register of Marine Species (WoRMS) and museum collections.Challenges in measuring body size include unique methods for different marine species.MOBS is used to analyze biases in species descriptions and provides a cost-effective research focus.The project offers a valuable platform for researchers amidst funding challenges in scientific research.The database is a key resource for exploring marine macroecology and macroevolution.