K.
Funny that you mentioned this, my 15 month old just started doing the same thing. I originally thought he just didnt want to get out of the tub or didnt want his diaper back on. I think I figured out that he is cold. I started wrapping him up in a towel and giving him a blanket when he is on the changing table, then I distract him with some singing or giggly stuff, and it has helped. I figured out the cold thing, when I noticed he was shivering in between crying screams. Anyway, hope this helps.
K.