Which ocean-energy device uses a submerged turbine moved by tidal currents to generate electricity?

A tidal-stream turbine uses a submerged turbine moved by tidal currents to generate electricity.

The device works much like an underwater wind turbine. As seawater flows through the rotor, its blades turn a generator, and the resulting electricity is carried to shore through subsea cables. Tidal currents are driven mainly by the gravitational interactions of the Earth, Moon, and Sun, making their timing highly predictable.

A tidal-stream turbine differs from a tidal barrage, which is a dam-like structure that creates a basin and generates power from changing water levels. It also differs from a wave-energy device, which captures motion at the ocean surface. Tidal-stream technology faces challenges including corrosion, installation, maintenance, marine navigation, and possible effects on local ecosystems.