Desalination is an idea that keeps reappearing in the Golden State, where overdrawn groundwater and shrinking reservoirs are critical problems. On a superficial level, it seems simple: take the salt out of the abundant salt water just offshore. But typical desalination facilities are big, expensive to operate, and environmentally unfriendly, especially when the resource-intensive process is powered by fossil fuels. The Carlsbad desalination plant in Southern California, for example, sits on 2.4 hectares of land and uses 246,156 megawatt hours of electricity per year—equivalent to the usage of roughly 23,000 homes.

Oneka’s experimental water desalination device isn’t like California’s other desalination plants: it’s a 6.5-meter-wide buoy. The small footprint is a bonus, but the device’s main advantage is that it’s ocean powered. As the buoy moves back and forth with the waves, it draws water through a filter and then through a reverse osmosis membrane, which removes the salts and other tiny particles. “Surprisingly simple,” says Smith.