A submarine or surface watercraft is equipped with at least one, preferably supercharged charging diesel engine, which serves to charge the vessel's batteries and which is operated in a controlled and regulated manner during submarine snorkeling mode or during the normal operation of surface watercraft. In at least one embodiment, the exhaust gases produced during the operation of the charging diesel engine are mixed with a flow of water, which is drawn from the water surrounding the vessel and delivered in a regulated manner by a pump while interacting with a negative-pressure generating device, and, in a mixed state, are discharged under water. The operation of the formed negative-pressure generating and mixing device ensues while interacting with the controlling and regulating of the charging diesel engine.