My first thought was, hey, as long as she's in the tub, she might as well do full immersion baptism of the ducks. Don't get me wrong, I'm no Alexander Campbell, but a full immersion seems to make the most of the sacramental sign.
My second thought was, Maia's little baptizing habit could become a problem. What if she's sharing the tub with an unbaptized sibling, and she decides to baptize him or her? Once she gets the Trinitarian formula down, would that be a valid baptism?
My third thought was, it's probably best that I not teach her full immersion baptism, given the sibling scenario... or how she might interact with kids in the Orchardly Park wading pool this summer. What would I say - "No, she's not trying to drown your son, she's just baptizing him?"
So there you have it. I'm not encouraging full immersion for Ms. Duck after all. Not to mention she has already been baptized. Not to mention she's a large rubber duck.