RE: Newbie to seaplanes
Without a water rudder, an idling plane will weathervane into the wind. Pull up elevator and add a little power so the rears of the floats dig in and the noses are reaching for the sky, and it will weathervane downwind. Carefully manipulating the throttle, you can find a balance that will let you taxi crosswind.
WITH water rudders, you can have so much water rudder authority that the plane will point downwind no matter what you do.
RULE #1: If your motor is running you can steer with the air rudder. If your motor is not running...it doesn't matter.