That seems a horribly complicated way of doing things. On the basis that hovercrafts always use "push" drive (or do they ?) there's no need to reverse the motor so all you need is a decent FET circuit and pulse modulate (PWM) it to vary the speed of the motor.
I agree. Furthermore, the L298N has a voltage drop of several volts between the battery and the motor, whereas a correctly-chosen mosfet will drop only a small fraction of a volt. Don't forget to connect a flyback diode in parallel with the motor.