This chapter surveys technologies that harness tidal flows in the ocean. It compares horizontal-axis turbines with vertical-axis designs suited to reversing and multidirectional currents, then novel concepts such as hydrofoils and tethered kites, and broadens to barrages and lagoons that exploit tidal range. Beyond device physics, it covers site considerations, installation and retrieval logistics, and lessons from past projects. The chapter closes with integration and storage strategies to mitigate variability and enhance grid services.