The invention relates to transportable and compact power supply unit for supplying a water vehicle, in particular an electrical power supply system of the water vehicle, with electrical energy and in particular for arrangement on the water vehicle, containing in a transport container or a plurality of transport containers that can be connected together, wherein the transport container or the plurality of transport containers can be transported as a single, coherent unit: at least one internal combustion engine that can be operated on gas, in particular a natural gas, at least one generator for generating power, which can be driven by the at least one internal combustion engine, at least one control device for the at least one internal combustion engine and/or at least one control device for the at least one generator, at least one fuel treatment device for the at least one internal combustion engine and/or at least one exhaust gas cleaning device for the at least one internal combustion engine, and at least one fuel storage device, wherein the fuel of the fuel storage device is a gas, in particular a natural gas, which is present preferably as liquefied gas, especially preferably as LNG.