The underwater electricity production module according to the invention includes means in the form of an elongated cylindrical box (12) in which means are integrated forming an electricity production unit including means forming a nuclear boiler (30), associated with electricity production means (37) connected to an external electricity distribution station by electrical cables, is characterized in that the nuclear boiler-forming means (30) are placed in a dry chamber (19) of the reactor compartment (18) associated with the chamber forming a safety water storage reservoir (20) of the reactor whereof at least the radial wall (53) is in a heat exchange relationship with the marine environment and in that the dry compartment (19) of the reactor container (18) is connected to the safety water storage reservoir chamber (20) of the reactor by depressurizing means (70) including means (71) forming a depressurizing valve placed in the upper portion of the dry chamber (19) and connected to one of the bubbler-forming means (72) placed in the lower portion of the storage reservoir chamber (20).