An underwater electricity production module includes an elongated cylindrical casing, which includes an integrated electricity generation unit having a nuclear boiler. The generator is connected to an external electricity distribution station by electrical cables. The nuclear boiler is placed in a dry chamber of a reactor compartment associated with a chamber forming a safety water storage reservoir of the reactor. At least a radial wall of the reservoir chamber is in a direct heat exchange relationship with a marine environment that surrounds the underwater electricity production module in which the underwater electricity production module is submerged.