NOVELTY - The apparatus (210) has a power generating module adaptably attached to a support structure (214) to form a fixed configuration and a rotatable configuration. An active lifting device places the power generating module in the rotatable configuration from the fixed configuration, where the power generating module is negatively buoyant. A clamping device is arranged to place the power generating module in the fixed configuration to prevent rotation. The lifting device includes a resilient bias. The lifting device comprises actuators, where the apparatus comprises a ballast system.    USE - Power generating apparatus such as non-buoyant generator and heavy sub-aquatic power generating apparatus e.g. tidal turbine generator, for use in tidal turbines for generating electricity for export into an electrical network or electrical grid.    ADVANTAGE - The support structure and the power generating module are physically connected in the fixed and rotatable configurations, so that the lifting device is arranged to urge, drive, push or thrust the support structure and the power generating module apart, thus reducing friction between contacting surfaces without physical separation. The apparatus provides a turbine with a bladed rotor, which is rotatably driven about a principal axis of the generator, so that rotational power generated between interaction of the flow of water and the rotor is harnessed within a housing of the turbine by driving an electrical machine, thus generating electricity for export into a network or grid in an effective manner. The hydraulic arrangement is used in conjunction with the power generating apparatus to provide a low friction interface between the mating surfaces, thus reducing required separation and amount of lift to be required from a biasing device or other lifting device.    DETAILED DESCRIPTION - The lifting device is a hydraulic arrangement. The support structure is formed as a columnar structure or pylon structure. The clamping device is a clamp. The resilient bias is a spring e.g. Belleville spring. An INDEPENDENT CLAIM is also included for a method for rotating a power generating apparatus.    DESCRIPTION OF DRAWING(S) - The drawing shows a side view of a sub-aquatic tidal turbine generator in a first orientation.    Power generating apparatus (210)    Turbine (212)    Support (213)    Support structure (214)    Sea bed (216)