A turbine has a flow pathway with an inlet in communication with the fluid channel. A rotor is disposed in the flow pathway and is rotatable around a rotation axis under the action of fluid flowing along the flow pathway. The rotation axis of the rotor is oblique to an axis extending along the fluid channel. The outlet of flow pathway may return fluid to the fluid channel. The turbine may also be provided with a flow control arrangement so as to vary the flow of fluid past the rotor and to prevent the rotor from damage. The rotor may be positioned apart from the fluid channel and so as not to obstruct the fluid channel.