Ocean currents have many profound impacts on marine life, moving not only animals and plants around the ocean but also redistributing heat and nutrients. While some of these impacts have been well known for many decades, there have been major recent developments in this area. Biologists are increasingly collaborating with physical oceanographers. At the same time, methods to accurately predict ocean currents and their variability have improved over a broad range of spatial and temporal scales. Emerging from these initiatives is an understanding of how currents impact the connectivity of marine populations, how they influence the migration of strong swimmers, including whales and turtles, and how changing currents, as part of global climate change, may re-shape entire communities. Graeme Hays introduces the ways in which ocean currents influence marine life.