As the bulge waves travel down the tube and arrive at the stern, the pressure in the chamber ahead of the power-take-off cycles above and below the tube’s rest pressure. During the high pressure part of the cycle, water passes through a set of non-return valves into an accumulator where pressure is allowed to build up. A smoothed flow of water then passes from the accumulator into a conventional hydraulic turbine which drives an electrical generator. On exit from the turbine, the water is accepted into a low pressure accumulator and is then drawn through another set of non-return valves back into the main tube during the low pressure part of the bulge wave cycle.