Cool water, remember you are 98.6* so if it feels warm to you, it's way too warm for him. Easy does it...preferably check the water temp.
Good luck with him, you'll need it, if he's in the condition you say.
And remember that a dehydrated snake cannot digest...water is more important, first, before feeding. Both mites & any internal parasites
are dehydrating him quickly, since he is small. This is basically an emergency, if you hope to save him.