That's good- let's hope it's just that he likes to soak because he's a blood python (but honestly, I'd keep checking anyway for the next month, just in case). When he's not in the water, wipe him gently with a damp white cloth to see if you snag any mites. I've only dealt with mites on 2 snakes, both many years ago. Never hurts to be suspicious though, they spread so easily.