A greater volume of air is entrained in the water flow from a hydrotherapy jet by directing the discharge from a first venturi nozzle through a second nozzle that constrains and accelerates the flow. For greatest aeration the ratio of the discharge orifice diameter for the first nozzle to that of the second nozzle is about 0.7-0.85, the ratio of the distance between the discharge orifices for the two nozzles and the diameter of the first nozzle's discharge orifice is about 0.85-1.5, air is introduced into the discharge from the first nozzle from a location fully behind that nozzle's discharge orifice, the flow of air to the downstream side of the second nozzle's discharge orifice is blocked, and the upstream end of the second nozzle overlaps the downstream end of the first nozzle.