A high-velocity water misting gun with a very high-speed radial inflow hydraulic turbine mounted on the same shaft with an axial flow air compressor wheel compressing air discharged at high velocities through an exhaust air nozzle. All of the water discharging from the hydraulic turbine wheel is channeled directly into a water misting nozzle providing a fine water mist discharging into a high-velocity air flow provided by the axial-flow compressor. Preferred embodiments utilize a manually operated ball valve to control water pressure supplied to the gun. A second valve is a manually operated turbine water bypass valve that is integral part of the preferred embodiment which allows for change of turbine power and air flow independently of water flow. With turbine water bypass valve open, most of the turbine flow is bypassed around the turbine and directly into the water misting nozzle, increasing the water flow and decreasing the air flow and air velocity. With turbine water bypass valve fully closed, hydraulic turbine power increases the power input into the compressor resulting maximum reach of the water-air mist jet.