A buoy system includes a sea-bed pump station having separate reservoirs of lighter-than-water and heavier-than-water liquids. The reservoirs are in fluid communication with peristaltic pumps that are operated via a preprogrammed control within the station. A buoy has an upper chamber connected by umbilical to be in fluid communication with the lighter-than-water chamber of the pump station and also includes a lower chamber connected to be in fluid communication with the heavier-than-water chamber of the station. The sea-bed and buoy chambers for the heavier-than-water liquid are both gimbaled mounted to assist fluid transfer even when non-level. Selected venting at the sea-bed pump station and of the buoy permit sea flooding and pressure equalization.