A subsea fluids storage facility comprises a tank (11) for holding and separating fluids which is equipped with ballast capacity (14) and a separable base (12) to be deployed upon the seabed in shallow or deep water, and the storage facility is connectable to a surface production facility, especially a buoy (24) for processing fluids. In deep water the tank (11) is held at a depth above the base (12) for temperature controlled stabilization of produced oil in the tank (11).