A wave-flow power installation comprises a float, a convergent-divergent water passage, attached to the float by an arm furnished with a hinge to turn the passage perpendicularly to a water stream, two turbines coaxially mounted in the passage, oriented orthogonally to the stream, each having a shaft oriented across the passage, an end of the shafts is attached to the wall of passage, supplied with hydro-dynamical blades, providing opposite rotation of the turbines, and an electro-generator including two rotors kinematically coupled with the shafts of the first turbines, providing rotation of the rotors in the opposite directions, and a stationary inductor disposed between the rotors. In some embodiments, the electro-generator is enclosed in a cavity of a hermetic capsule. The present invention can be used for building non-polluting power plants on rivers, in coastal areas of sea, and in proximity to platforms for underwater extraction of minerals.