If his head goes under water and he doesn't like it he'll lift it back up. Instead of the bath tub try soaking him in a smaller tub (like a plastic one with a lid). He'll be able to feel the sides with his body and feel a little more secure. The water only needs to be about half way or 2/3 up his body.
And back to the enclosure, is that Aspen bedding? If so ditch that and get something like cypress mulch or Coco block and return the fogger. Aspen holds no humidity and if it gets too wet (like from the fogger) it can mold.