This ball python is in critical condition! I think you should definitely take him to a herp vet but how long have you had him? Petco usually has a 30 day guarantee on animals that can be returned if they are unhealthy. They need to be alerted about this. I can't believe he was sold being so emaciated. Time is of the essence right now. Soaking is a appropriate measure for this animal but water should be about 80.0f and the water level should only cover his ventral scales. Ball pythons do absorb water through the cloaca. Probably would be a good idea to mix 50% pedialite solution at the same temperature. However in this case you have to be sure to keep his head above water bc he doesn't seem strong enough to hold himself up. Wow! Good luck and I hope he can bounce back.