Abstract: The invention relates to a screw propeller and its variants for converting mechanical energy in a fluid medium, and can be used in the form of water and air screws for engines and propulsers, making it possible to simplify the production method of propeller blades, to reduce the dimensions and material consumption of propeller blades, and to simultaneously increase a thrust produced thereby without decreasing the strength and efficiency thereof. The inventive propeller comprises at least two scimitar-shaped blades whose basic sections are fixed to the hub of a driven shaft. The basic section of each blade is straight and scimitar in shape, wherein the front edge of the blade is bent backwards in relation to the direction and plane of rotation and gradually transforms into the inverse, scimitar-shaped end section. Moreover, the front edge of the blade is forwardly bent in relation to the direction and plane of rotation.