Abstract: An apparatus for generating electricity from a bidirectional water flow, such as tidal flow, includes a base structure, a primary flow pipe defining a first flow passage through the base structure, and a secondary flow pipe defining a second flow passage through the base structure. The primary flow pipe includes a convergent section a mixing chamber, the convergent section connected to a first end of the mixing chamber to define a venturi therebetween, and a diffuser section connected to a second end of the mixing chamber. The apparatus further includes an opening in the secondary flow pipe to provide fluidic communication between the second flow passage and the mixing chamber, a turbine connectable to a generator and arranged to be rotated by water flow from the second flow passage, and a control mechanism for directing the water flow from the second flow passage through the opening into the mixing chamber.