A propeller with folding blades for the propulsion of a mobile vehicle inside a fluid is provided having a movement mechanism rotatable around a central rotation axis of the propeller; and a plurality of blades. Each blade has a root end connected to the movement mechanism by a gear to allow the movement of the blade from an opening position to a closed position and vice versa, wherein in the closed position the plurality of blades are configured to form a continuous solid in the form of a spindle wherein a leading edge of a first blade (S) is configured to osculate a trailing edge of a second blade following the first blade (S) in such a way as to form a continuous surface between the first blade (S) and the second blade (S).