TECHNOLOGY FOCUS - MECHANICAL ENGINEERING - Preferred Device: The desalination device further comprises an input filter (12) for removing particulate debris or suspended solids contained within the body of water. The water engine comprises at least one water driven member mechanically connected to the hydraulic rams. The water driven member comprises a float chamber, a float, an input gate valve, or an output gate valve. The input and output gate valves comprise a butterfly valve or a non return valve (13-17). A changing geometry headgear connects the floats of at least two water driven members and comprises a pivotally mounted beam comprising an extendible post associated with each water driven member such that the post adjustably connects to the associated float allowing the position of the float to be adjusted relative to the associated float member. The desalination device further comprises a device input valve for controlling the liquid supplied to the hydraulic rams. The hydraulic rams comprise an input port and an output port that move between an open and a closed position to provide mechanism for controlling the flow of the liquid through the hydraulic rams. The reverse osmosis unit further comprises a second reverse osmosis filter which acts to filter a permeate produced by the first reverse osmosis filter (18). An exhaust liquid from the second reverse osmosis filter is stored within a liquid reservoir (29) to provide a second liquid source for the hydraulic rams. The device further comprises a hydraulic motor that is driven by an exhaust liquid from the first reverse osmosis filter. It further comprises a control valve (24) and double acting hydraulic ram. The control valve comprises a three position four port valve. It further comprises a low pressure pump (12) powered by the hydraulic motor (20) to draw the body of water through the input filter, thus supplying the liquid to the hydraulic rams; a high pressure pump (31) powered by the hydraulic motor to draw the body of water through the input filter thus providing a second high pressure liquid supply to the hydraulic accumulator; an electrical generator and a rechargeable battery; and diagnostics for monitoring the operation of the device.