Everything seems to be listed as stressful to a ball python. Its an ironic twist that the most highly bred snake with the most hereditary color mutations, and also the most widely sought after snake is also the biggest head case of any herp IMO.

IMO soaking is fine. If hes not thrashing around and calms down after a bit I wouldn't worry. Make sure that he doesn't have to swim the whole time and that the water isn't too deep.