Especially when prey is thawed in water, some of us have pointed out that the extra moisture does help with hydration for the snake, but it's never enough to make up for the amount needed to digest; digestion requires extra moisture from the snake's body, & so does shedding. Doing both simultaneously is a bad idea for snakes whose humidity has not been optimal, OR, if their diet hasn't been adequate: for example, a poorly fed snake may need time to replenish their digestive enzymes...to do that requires good quality food & enough of it. (This is why snakes that have been fed pinky rodents when they should have moved up to more appropriately-sized prey may also have trouble shedding...it may not be a lack of hydration but due to a nutritional lack instead.)