摘要：

A device for extracting energy from a water body ( 4 ) comprises a buoyant member of variable buoyancy ( 6 ) which is at least partially submerged in the body of water ( 4 ). The buoyant member of variable buoyancy ( 6 ) contains a fixed mass of gas ( 7 ), the volume of which changes as a result of the pressure changes exerted on the buoyant member ( 6 ) by waves ( 10,11 ) and/or other changes in the water level above. The buoyant member ( 6 ) is preferably constructed from a substantially air-tight, flexible or otherwise elastic material, whereby the volume of the buoyant member of variable buoyancy ( 6 ) may alter in response to changes in the volume of gas ( 7 ) contained therein. The pressure changes result in volume changes of the gas contained within the variably buoyancy, which causes fluctuations in volume of the variable buoyancy. As a result of changes in volume a change in buoyancy occurs. This results in a corresponding change in upthrust exerted by the variable buoyancy ( 6 ) which affects the forces exerted on an energy conversion unit ( 8 ).

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