Looking to leverage all that motion in the ocean is UK startup Sustainable Marine, whose floating tidal turbine rotors just breezed through a testing regime that simulated 20 years of real-world conditions.The biggest tidal energy systems in action today rely on big and expensive underwater walls, with sluice gates that open and close as the tide changes and leverage the varying water levels to turn turbines. A different approach is to use floating platforms that can be towed out into channels with accelerated tidal flows and moored to the ocean floor. These use turbines attached to massive arms that are plunged into the underwater currents to generate power, and present a potentially far cheaper way forward.