A reduced pressure mixing device is for marine vessel exhaust gas with water, with the gas/water mixture that is produced in the device being passed out into the water in which the ship is floating. The device is designed such that gas and water flow through and to it longitudinally. Further, the device includes a centrally-arranged gas guide tube for the marine vessel exhaust gas as well as a propulsion water tube which is arranged coaxially around the gas guide tube and produces reduced pressure, with the tubes being located in an elongated housing.