A method for controlling the hybrid drive system of a water craft, comprising a combustion engine (1), an electric engine/generator (2), a drive train (5) having a propeller (7) and a storage battery (3), a control unit (8) and a clutch (4). In order to increase efficiency, during travel in the upper power range the electric engine (2) is additionally operated as a generator, and during travel in the middle and lower power ranges the electric engine (2) is operated with current from a storage battery (3). The drive train is designed so that the characteristic (20) thereof lies by a defined charging capacity below the point of minimum specific fuel consumption (e.g. 25), or is steeper than the characteristic (16) of a conventional construction.