Device for generating hydroelectric energy making use of the current of a river (11), estuary or similar, and this device comprises a paddlewheel (2) that can freely turn in two directions around a shaft X-X′, and comprises at least one electricity generator set (4) whose drive shaft (8a) is coupled to the shaft (3) of the paddlewheel, whereby the device (1) is further provided with means to keep the paddlewheel (2) in place against the current, characterized in that the paddlewheel (2) is self-floating.