Collecting oceanographic data from ice-filled polar waters is costly and logistically challenging. Rather than relying solely on human scientists, this project uses beluga whales and four seal species as ocean explorers to collect information about the conductivity (salinity), temperature and depth (CTD) of Arctic and Antarctic waters. By fitting state-of-the-art CTD tags on dozens of these deep-diving marine mammals, scientists will be able to gather a rich new data set that will extend our knowledge of the world's oceans as well as the top predators that live in them. MEOP will provide a unique source of fundamental physical and biological data from the polar oceans. Its unique approach will compliment efforts in many other IPY projects and will leave a legacy of useful biological and ocean data along with new approaches to understanding the interaction between marine predators and their ecosystem.