Jellyfish are important in the ocean ecosystem, but their role is not well understood. A new study used a global model to show that jellyfish have a unique distribution and biomass compared to other organisms. When jellyfish are included in the model, they directly affect crustacean zooplankton and indirectly influence the rest of the plankton community. This suggests that jellyfish play a crucial role in regulating marine ecosystems worldwide, impacting community structure, dynamics, and biomass.