A propeller has a number of blade surfaces or winglets extending helically around its rotational axis in the most streamlined manner. The winglets gradually project at an increasing distance outward with an arcuate shape, each defining a rearwardly concave channel that increases in volume and degree of encirclement rearward on the propeller. In the front of the propeller, the winglets are shaped so that they have edges angled obliquely and diagonally that conformingly and without cavitation cut into the water and cause it to flow smoothly in the channels. In the middle of the propeller, the winglet edges extend rearward so that water entrained in the channel is directed rearward without centrifugal loss. In the rear portion of the propeller, the channels narrow and reduce in volume so as to expel the water from the concavity.