NOVELTY - The machine (1) has a propeller shaft (4) coupled with a propeller (3), mounted within an underwater housing (2) and guided from the housing over a depressing opening (5). A transmission (6) formed as a planetary gear is coupled with the shaft and an electrical motor (11) and arranged within the housing. A shaft sealing system (9) seals the opening against a liquid entry into the housing. A transmission housing (7) of the transmission is partially filled with a transmission liquid (8), and the shaft sealing system lies at the transmission housing or is integrated into the transmission housing.    USE - Fluid-flow machine e.g. driving device such as rudder propeller or pod drive, pump, fan, compressor and turbine for a floating or submersible device e.g. ship and offshore platform, and for electricity production in a current power plant, tidal power plant or wind turbine (all claimed).    ADVANTAGE - The transmission housing of the transmission is partially filled with the transmission liquid, and the shaft sealing system lies at the transmission housing or is integrated into the transmission housing, thus easily transferring heat from the seal to the transmission fluid by the developing direct thermal contact between the seal and the transmission liquid for dissipating the heat of the seal more than the air located inside the housing if the transmission is arranged at distance from the shaft sealing system, and hence reducing risk of leakage of the seal, and reducing difference of pressure lies at the shaft sealing system and the mechanical load of the seal. The electrical motor is arranged within the housing, thus preventing liquid e.g. sea water from penetrating from the outside into the housing and preventing directly contacting of the electrical motor with the liquid, and hence permitting the electrical motor to be better protected from the penetrating liquid.    DESCRIPTION OF DRAWING(S) - The drawing shows a simplified partial longitudinal sectional view of a fluid-flow machine.    Fluid-flow machine (1)    Underwater housing (2)    Propeller (3)    Propeller shaft (4)    Depressing opening (5)    Transmission (6)    Transmission housing (7)    Transmission liquid (8)    Shaft sealing system (9)    Electrical motor (11)