Making it clear just how easy it is for his father to lift him up and then plunge him down into the bathtub drives home just how powerless the narrator is. He’s a child, so he’s small compared to a full-grown man, and he never imagined that his parent would do this to him. It recalls his visit to the wax museum, where his takeaway was that parents kill their children for anatomy—in these situations, parents have complete control over their children’s lives, even deciding whether they live at all.