I just had a thought that made me think of this post, it might be an idea to try with Zippy if he is food motivated!
Why not try getting a big, wide bowl, heavy enough that he can perch on, and fill it 2 inches with water, and float buoyant fruit on the surface? Like apples, cranberries, blueberries, whatever! I was thinking of kids bobbing for apples. I know his beak is more adept at picking stuff like that out of water but I thought it might be a fun way to get him used to dipping his face and chest in the water for a reward?
Might not work but could be worth a try!!