When a system of many individuals is under stress, whether seeking resources or avoiding threats, its survival depends on its ability to collectively move towards a specific objective. In many cases, either the objective itself or the environment in which this locomotion occurs is fluid, examples include large systems like human populations migrating in response to climate change, or microscopic systems like viruses navigating through the body to infect host cells. These complex events are often difficult to study directly due to their infrequency, experimental complexity, or the many scales involved. A large scientific community is working on solutions to better model and predict these collective motions. This project aims at understanding how cooperation between many individuals enables efficient locomotion towards an objective in a complex flow.