Abstract: A method compressing a gas, advantageously air, is disclosed. The gas is compressed by disposing one or more hydrofoils in a liquid flow for the purpose of generating a downpull and thereafter a lift by altering the angle of attack on the hydrofoil relative to the flow of liquid, advantageously water. The down force causes the load, advantageously air, to be submerged, and hence compressed proportional to the depth of liquid to which the air is subjected. The hydrofoil is attached to a mechanical device, which in turn is anchored or moored in the depth of the liquid and at or under the surface. The angle of attack of the hydrofoil is altered by mechanical devices connected to tension bars or strings or by flaps. The volume of air loaded in the hydrofoil is adapted such that the down force is greater than the buoyancy of the air. An accelerating effect is achieved by that the volume of air decreases inversely proportional to the increasing depth to which it is subject.