Mixing apparatus is disclosed suitable for the mixing and/or aeration of large bodies of water e.g. lakes or reservoirs. One particular use is in causing controlled destratification. Another area of use is in the aeration or oxygenation of liquid waste. The mixing apparatus has a draft tube (1) with an open interior, and gas injectors (6) to drive an upward flow of liquid through the draft tube (1). An arrangement of angled vanes (4) at the intake of the draft tube imposes swirl on the flow, which then rises unobstructed through the draft tube (1). No moving parts are involved.