a body defining a cavity, the body terminating in a distal open end that is adapted, in use, to be in the vicinity of a surface to be treated such that the surface forms a first end wall of a chamber within the cavity;

an acoustic transducer mounted to the body proximate n opposite second end wall of the chamber, the acoustic transducer being adapted to introduce acoustic energy into the chamber which is directed from the second end wall towards the first end wall thereby to allow acoustic pressure fluctuations to be generated at the surface to be treated, the acoustic pressure fluctuations being sufficient to cause cleaning of the surface to be treated;

a reservoir for a liquid including an inlet passage for liquid flow into the reservoir and an outlet passage for liquid flow from the reservoir into the chamber; and

a liquid conditioning unit adapted to remove bubbles from the liquid supplied to the chamber, wherein the liquid conditioning unit has an input for liquid and an output for liquid, the output being connected to the inlet passage of the reservoir, wherein the liquid conditioning unit comprises a casing having a plurality of compartments serially located between the input and output, at least one of the compartments including a headspace at an upper part thereof for collecting gas released from liquid flowing through the liquid conditioning unit,

wherein the liquid conditioning unit is fitted to the body by a gimbal mechanism to permit the liquid conditioning unit to pivot relative the body so that when the liquid conditioning unit is submerged in water, the headspace is maintained in an upwardly oriented position by buoyancy of the headspace in the water.