Blue foods — aquatic foods captured or farmed in marine and freshwater systems — play a key role in feeding and nourishing the world by providing highly accessible and affordable sources of protein and micronutrients for over 3.2 billion people and supporting the jobs of 58.5 million people, and the livelihoods of 600 million people. In the past 71-year period, blue foods have significantly expanded from 19.9 million tons in 1950 to 214 million tons in 2020. Yet, with 811 million people suffering from hunger and 3 billion people unable to afford a healthy diet, blue food production is poised to continue to expand in the future. However, the expansion of aquaculture and fisheries has also raised a series of ecological and environmental issues, such as biodiversity loss, environmental pollution (plastic pollution, antibiotic pollution, nitrogen and phosphorus emissions, etc.), land and freshwater use, overfishing, habitat degradation etc. In parallel, the continuously growing demand for blue food has been challenged by unprecedented environmental changes, such as climate change, ocean acidification, water pollution (microplastics, antibiotics, persistent pollutants), etc. But compared to other animal-sourced foods, blue food can remain an imperative component of sustainable food system solutions by reducing the environmental footprint and relieving pressure on overburdened terrestrial systems. Therefore, it is important to understand the challenges and priorities of the blue food transformation in order to jointly promote food safety and environmental sustainability.