A method for reducing the lifting force during the lowering of a load onto an underlay by a lifting device, wherein the method comprises in successive order: A) utilising a heave compensating device comprising: - a length extension device having an upper and a lower end and which has an upper vacuum chamber and a lower liquid filled chamber due to a slideable piston having a piston rod which stretches through the lower liquid filled chamber and further out a distance through a fluid tight opening in the lower end of the length extension device and ends in a releasable attachment device, and - an elongated gas accumulator having an upper chamber and a lower liquid filled chamber divided by slideable piston, and where the lower liquid filled chambers (5, 15) of the length extension device and the gas accumulator are fluidly connected to each other by a liquid transferring device, and where the upper chamber has a, with a first valve, adjustable gas outlet, and - a gas tank having an expansion chamber fluidly connected to the upper chamber of the gas accumulator by a, with a second valve, adjustable gas outlet, where the gas outlet of the expansion chamber of the gas tank is fluidly connected to the gas outlet of the upper chamber of the gas accumulator by a gas transferring device, and - a, with a third valve, adjustable gas outlet to the environment fluidly connected to the gas transferring device, B) introducing a sufficient amount of gas into the expansion chamber of the gas tank, and introducing a sufficient amount of gas into the upper chamber of the gas accumulator to form a gas pressure which at least is able to obtain an intended equilibrium position of the piston of the length extension device when the full sensible weight of the load is pulling on the piston rod, and thereafter closing all gas outlets (23, 25, 32) by closing the first, second and third valve, C) attaching the upper end of the length extension device to the lifting device and the load to the attachment device of the piston rod, characterised in that the method additionally comprises the following step, when reducing the lifting force is to be obtained: M) opening for gas flow through the gas transferring device between the upper chamber of the elongated gas accumulator and the expansion chamber of the gas tank such that the gas pressure of these chambers (22, 29) is equalised. A) utilising a heave compensating device comprising: - a length extension device having an upper and a lower end and which has an upper vacuum chamber and a lower liquid filled chamber due to a slideable piston having a piston rod which stretches through the lower liquid filled chamber and further out a distance through a fluid tight opening in the lower end of the length extension device and ends in a releasable attachment device, and - an elongated gas accumulator having an upper chamber and a lower liquid filled chamber divided by slideable piston, and where the lower liquid filled chambers (5, 15) of the length extension device and the gas accumulator are fluidly connected to each other by a liquid transferring device, and where the upper chamber has a, with a first valve, adjustable gas outlet, and - a gas tank having an expansion chamber fluidly connected to the upper chamber of the gas accumulator by a, with a second valve, adjustable gas outlet, where the gas outlet of the expansion chamber of the gas tank is fluidly connected to the gas outlet of the upper chamber of the gas accumulator by a gas transferring device, and - a, with a third valve, adjustable gas outlet to the environment fluidly connected to the gas transferring device, - a length extension device having an upper and a lower end and which has an upper vacuum chamber and a lower liquid filled chamber due to a slideable piston having a piston rod which stretches through the lower liquid filled chamber and further out a distance through a fluid tight opening in the lower end of the length extension device and ends in a releasable attachment device, and - an elongated gas accumulator having an upper chamber and a lower liquid filled chamber divided by slideable piston, and where the lower liquid filled chambers (5, 15) of the length extension device and the gas accumulator are fluidly connected to each other by a liquid transferring device, and where the upper chamber has a, with a first valve, adjustable gas outlet, and - a gas tank having an expansion chamber fluidly connected to the upper chamber of the gas accumulator by a, with a second valve, adjustable gas outlet, where the gas outlet of the expansion chamber of the gas tank is fluidly connected to the gas outlet of the upper chamber of the gas accumulator by a gas transferring device, and - a, with a third valve, adjustable gas outlet to the environment fluidly connected to the gas transferring device, B) introducing a sufficient amount of gas into the expansion chamber of the gas tank, and introducing a sufficient amount of gas into the upper chamber of the gas accumulator to form a gas pressure which at least is able to obtain an intended equilibrium position of the piston of the length extension device when the full sensible weight of the load is pulling on the piston rod, and thereafter closing all gas outlets (23, 25, 32) by closing the first, second and third valve, C) attaching the upper end of the length extension device to the lifting device and the load to the attachment device of the piston rod, M) opening for gas flow through the gas transferring device between the upper chamber of the elongated gas accumulator and the expansion chamber of the gas tank such that the gas pressure of these chambers (22, 29) is equalised.