Four Wave Gliders — self propelled robots, each about the size of a dolphin — left San Francisco on Nov. 17 for a 60,000 kilometer journey, IEEE Spectrum Automation reports.

Built by Liquid Robotics, the robots will use waves to power their propulsion systems and the Sun to power the sensors, as a capability demonstration. They will be measuring things like water salinity, temperature, clarity, and oxygen content; collecting weather data, and gathering information on wave features and currents.

The data from the fleet of robots is being streamed via the Iridium satellite network and made freely available on Google Earth’s Ocean Showcase.