You can steer with the air rudder, elevator, and throttle.

To go upwind, just let go with lo idle or stopped motor and the plane will weathervane into the wind.

To go downwind, hold full UP, add about 1/3 throttle. and the plane will lift up onto the tail end of the float, and will weathervane downwind.

Reducing the throttle some lets the front part of the float find its way back to the water....by careful manipulation of the throttle(Still holding up elev) you can balance the tendency to turn upwind or downwind, and steer with the throttle and with almost no correction from the rudder.

People put water rudders on their floatplanes planes and expect to drive them around like RC Cars....it doesn't happen.

If you have propblast over your air rudder, you can steer without a water rudder. If there is no propblast...it doesn't matter.