The inventive nozzle comprises a first releasing stage (1) for producing a pre-release by absorbing from 5 to 20% of available pressure, a second releasing stage (2) wherein a substantial release is carried out and the pressurised water passes from a saturation pressure to an output nozzle pressure, an intermediate chamber (3) in the form of a transition chamber in which the pressurised water approaches the saturation pressure by absorbing from 5 to 30% of the available pressure and an outlet tube (3) consisting of a sudden release and cavitation confinement tube whose minimum length (1) substantially corresponds to a distance separating the end of said tube on the second release stage side from a readhesion point of jets to the tube wall at the angle of divergence (alpha) thereof ranging from 3 to 12 DEG before readhesion.