I would not put anything in the water with the snake. While you should be watching it you don't need it to get under the towel or cloth and not find his way out. He could drown. The proper way to soak a snake is to place it in water no deeper than their body. I usually only go half to 3/4 up their body. That way they soak but do not have to fight to keep their head above water. If the water is shallow as it should be the snake will not need anything to rest on. If it needs such a think the water is deeper than it should be.