A water vehicle-actuated air compressor and a system are disclosed for utilizing compressed air to operate an electrical generator to generate electricity. The water vehicle-actuated air compressor includes an actuator, a cylinder, and a piston in the cylinder reciprocable in response to actuation of the actuator by the motion of the vehicle through the water for compressing air in the cylinder. The cylinder is provided with a first vent means for introducing air into the cylinder behind the piston during a forward stroke of the piston, a valve-controlled second vent means for introducing air into the cylinder on the other side of the piston during the reverse stroke thereof, and outlet means for supplying air compressed by the piston during the forward stroke thereof to a utilization device. In the system for generating electricity, the air compressor is combined with an electricity generator operated by compressed air to generate electricity and at least one air storage unit coupled between the electricity generator and the outlet means of the cylinder for storing compressed air enroute to the generator. The air storage unit may be supplied with compressed air from other vehicle-actuated air compressors to provide a network for supplying compressed air to the air operated electricity generator.