The various turbine rotor options are, as has been said for some time, quite similar to those for wind turbines, the horizontal axial-flow turbine and the Darrieus or cross-flow turbine. In the latter type, blades rotate perpendicularly to the flow.
Options to secure a rotor include mounting the unit beneath a floating pontoon or buoy, suspending it from a tension leg arrangement between an anchor on a seabed and a flotation unit on the surface (as has been proposed in the past), or seabed mounting, easy only in shallow environments.[222]
